New York (CNN) -- Police investigating the death of actor Philip Seymour Hoffman have found close to 50 envelopes of what they believe is heroin in his Manhattan apartment, two law enforcement sources familiar with the inquiry said Monday.
A number of used syringes, prescription drugs and empty bags that authorities suspect used to hold heroin also were found in the apartment where Hoffman, 46, was found dead Sunday of an apparent drug overdose on the bathroom floor with a syringe in his left arm, the sources said.
The New York medical examiner's office is conducting an autopsy, according to law enforcement sources.
"We are devastated by the loss of our beloved Phil and appreciate the outpouring of love and support we have received from everyone," Hoffman's family said in a statement. "This is a tragic and sudden loss and we ask that you respect our privacy during this time of grieving."
The Oscar-winning actor last talked with someone at 8 p.m. Saturday, as far as authorities have determined, a law enforcement official said.
He was expected to pick up his children Sunday but didn't show up, the official said. Playwright David Katz and another person went to the apartment and found him dead, the official said.
Police officers found him in a T-shirt and shorts with his eyeglasses still on his head.
Police also found several empty bags branded "Ace of Hearts" -- a street name for heroin -- in the apartment, two law enforcement sources familiar with the investigation told CNN.
Also in the apartment were close to 50 envelopes, branded "Ace of Spades," containing what is believed to be heroin, the two sources said.
Investigators also found in the apartment, which was leased from a friend, according to the two sources:
• More than 20 used syringes in a plastic cup.
• Several other bags containing white powder.
• Prescription drugs, including the blood-pressure medication clonidine hydrochloride; the addiction-treatment drug buprenorphine; Vyvanse, a drug used to treat attention-deficit (hyperactivity) disorder; hydroxyzine, which can be used to treat anxiety; and methocarbamol, a muscle relaxer. Authorities are investigating whether Hoffman had prescriptions for these drugs, the sources said.
Timeline of Hoffman's final days, hours
The law enforcement sources told CNN that investigators have begun to piece together where Hoffman was in the days before his death by talking to his family and friends.
An assistant for Hoffman told police she saw him Friday at his apartment and there was nothing out of the ordinary. He also seemed fine when she spoke to him on Saturday at about 1:30 p.m. ET.
But Mimi O'Donnell, Hoffman's ex-partner, told authorities that when she saw him near his apartment at 2 p.m. Saturday she thought he appeared to be high.
O'Donnell said she spoke with him on the phone about six hours later and again thought he seemed high, the sources said.
The next morning, on Sunday, Hoffman failed to show up at her home to pick up their three children.
At 11 a.m. she asked Katz to go to Hoffman's apartment. He called police 30 minutes later.
Investigators, working on the theory that Hoffman's death was a drug overdose, are now trying to find exactly where he bought the drugs, the sources said.
This will involve searching his phone in addition to tracking his movements, the sources told CNN.
Authorities also are looking into whether anyone was with the actor when he died, law enforcement officials said.
Hoffman loved 'deep, dense characters'
Hoffman won an Academy Award for best actor for the 2005 biopic "Capote" and drew critical acclaim for his roles in a wide variety of films.
He was a beefy 5-foot-10-inch man but was convincing as the slight, 5-foot-3-inch Truman Capote. He had a booming voice like a deity's but often played schlumpy, conflicted characters.
"He just loved those deep, dense characters. That's where I think he found his true calling," said Bradley Jacobs, a senior editor of Us Weekly.
Hoffman's big break in Hollywood came with a small role as Chris O'Donnell's classmate in the 1992 film "Scent of a Woman."
For years, Hoffman was the kind of anonymous character actor who earned critical raves but was often unnoticed by the general public. He used his abilities to take chances with such directors as a then-unknown Paul Thomas Anderson, with whom he worked in "Hard Eight" (and several ensuing films) and Todd Solondz ("Happiness").
"I think about that a lot," he told Esquire in 2012 of his anonymity. "I feel it cracking lately, the older I'm getting. I think I'm less anonymous than I was."
As an actor, Hoffman could be heartfelt and giving, as with his male nurse in "Magnolia" or rock critic in "Almost Famous," or creepily Machiavellian, like the gamemaster in the latest "Hunger Games" movie or a "Mission: Impossible" movie villain.
Cameron Crowe, who directed "Almost Famous," said a notable scene in which Hoffman's character Lester Bangs speaks with a young journalist about being uncool was not what Crowe had initially envisioned. He said in between takes Hoffman listened through his headphones to taped interviews with Bangs, a well-known rock music writer who died in 1982. Hoffman didn't speak.
"When the scene was over, I realized that Hoffman had pulled off a magic trick. He'd leapt over the words and the script, and gone hunting for the soul and compassion of the private Lester, the one only a few of us had ever met," Crowe wrote on his website. "The crew and I will always be grateful for that front-row seat to his genius."
Hoffman also appeared in "Charlie Wilson's War," "Doubt" and "The Master," for which he was nominated as best supporting actor.
He appeared last month at the Sundance Film Festival, where a movie he starred in, "God's Pocket," premiered.
"He seemed really in good spirits, and it's just so shocking," said CNN Entertainment commentator Krista Smith, who interviewed Hoffman at the festival. "Because, just looking at his body of work and knowing how many actors revered him and how they look up to him. ... The one thing that was so special about him is that he crossed all platforms. ... Every genre, he managed to fit in and just be brilliant at whatever he was doing."
Beloved resident of New York neighborhood
But despite his love of performance, Hoffman was a private person who rarely spoke about his family, Jacobs said.
In New York's Greenwich Village neighborhood, where he lived, it was common to see the actor riding a bicycle and walking his children to the public school they attended.
"He'd go quietly about his business with his children. I still remember the day he won the Oscar, him walking his kids to school, not long after. And people were giving him high fives," said CNN's Rose Arce, whose daughter attended school with Hoffman's children.
After his Oscar win at the Academy Awards in 2006, Hoffman thanked his mother for taking him to his first play.
"She brought up four kids alone, and she deserves a congratulations for that. ... And she took me to my first play, and she stayed up with me and watched the NCAA Final Four, and my passions, her passions became my passions. And, you know, be proud, Mom, because I'm proud of you, and we're here tonight, and it's so good," he said in his acceptance speech.
Hoffman's father was a salesman, and his mother was a family court judge, according to a biography on the Turner Classic Movies website. He landed his first professional stage role before graduating from high school and went on to study acting at New York University.
Hoffman stayed active on stage even as his star rose in Hollywood. He starred in a Broadway production of "Death of a Salesman" in 2012 and was co-artistic director of the Labyrinth Theater Company in New York.
Last year, Hoffman revealed that he had entered rehab to deal with a drug problem, telling TMZ that he'd kicked a substance abuse habit for 23 years but recently relapsed.
In a 2011 interview with "60 Minutes," he discussed his past struggles with drug and alcohol addiction.
"Anything I could get my hands on, I liked it all," he said.
Asked why he decided to sober up, he replied, "You get panicked. ... I was 22, and I got panicked for my life, it really was, it was just that. And I always think, 'God, I have so much empathy for these young actors that are 19 and all of a sudden are beautiful and famous and rich.' I'm like, 'Oh, my God. I'd be dead.' "
According to TMZ, Hoffman said last year that he'd fallen off the wagon, started taking prescription pills and slipped into snorting heroin.
The actor's public comments about his battle with substance abuse illustrate the struggles many addicts face, according to HLN's Dr. Drew Pinsky, an addiction specialist.
"Someone with opiate addiction, they are doing pushups their whole lives. And they must work on it all the time. And even working on it, there's a high probability of relapse. And God willing, they get adequate treatment, and they re-engage in treatment, and things go well," Pinsky said. "But often, it's a frequently fatal condition. We just simply have to continually remind ourselves of that. And now it has taken a glorious, glorious talent from us."
After he returned from rehab, Hoffman rented the apartment where his body was found Sunday, two neighbors said. The rest of his family lived elsewhere in the neighborhood.
'He was a giant talent'
Word of Hoffman's death sparked a flood of reactions from actors, directors, studio chiefs and fans.
"This is a horrible day for those who worked with Philip," actor Tom Hanks said in a prepared statement. "He was a giant talent. Our hearts are open for his family."
Lionsgate, the studio behind "The Hunger Games" movies, described Hoffman as "a singular talent and one of the most gifted actors of our generation."
Robert De Niro, who starred opposite Hoffman in the 1999 movie "Flawless," said he was "very, very saddened" by Hoffman's death.
"This is one of those times where you say 'this just shouldn't be. He was so young and gifted and had so much going, so much to live for.' "
For Mike Nichols, who directed Hoffman in his Oscar-nominated turn in "Charlie Wilson's War," there were no words, just grief.
"No words for this. He was too great and we're too shattered," he said in an e-mailed statement.
Heroin use on the rise, authorities warn
Authorities have warned that heroin addiction is soaring and noted an uptick in the availability of the drug.
Last week, the Drug Enforcement Administration announced a heroin mill bust in the Bronx, New York, after the agency seized $8 million worth of the drug.
The DEA has warned that people who are addicted to opioid prescription pills are now finding highly pure heroin easier and cheaper to obtain.
It produces a similar, if more dangerous, high because unlike with the pills, there is no way to regulate the dosage of heroin, given the undetermined purity.
CNN's Jennifer Henderson, Chelsea J. Carter, Susan Candiotti, Todd Leopold, Carolyn Sung, Matthew Carey, Evan Perez and Jason Hanna contributed to this report.