Santa Maria, Brazil (CNN) -- Workers combing through the charred wreckage of Kiss nightclub in southern Brazil on Sunday encountered the eerie sound of ringing cell phones.
Glauber Fernandes, a reporter from CNN affiliate Band News, explains.
"It was a really complicated scene. A lot of smoke, a lot of shoes that was left, cell phones, because everybody tried to get out of there running," he said. "While we were there, we saw the cell phones were ringing. It was parents, friends, trying to know about what was happening and nobody was answering."
A fire swept through the packed, popular nightclub in Santa Maria early Sunday, killing at least 233 people -- enough to fill a large plane -- Brazilian Health Minister Alexandro Padilha told reporters. Of those, 185 have been identified so far.
Many apparently died from smoke inhalation. Others were trampled in the rush for the exits, one security guard told Band News.
More than 90 people were hospitalized, Padilha said, including 14 patients with severe burns.
About 2,000 people were inside the club when the fire broke out -- double the maximum capacity of 1,000, said Guido de Melo, a state fire official.
Investigators have received preliminary information that security guards stopped people from exiting the club, he told Globo TV.
"People who were inside the facility informed us ... that security guards blocked the exit to prevent people there from leaving, and that's when the crowd starting panicking, and the tragedy grew worse," he said.
The fire started "from out of nowhere" on a stage at the club and quickly spread to the ceiling, witness Jairo Vieira told Band News.
"People started running," survivor Luana Santos Silva told Globo TV. "I fell on the floor."
There was a pyrotechnics show going on inside the club when the fire started. Authorities stopped short of blaming it for the blaze, saying the cause was still under investigation.
The Kiss nightclub is popular with young people in Santa Maria, which is home to a number of universities and colleges, including the Federal University of Santa Maria. At least 80 of those killed Sunday were students at that school, it said.
The blaze broke out during a weekend when students were celebrating the end of summer. Many universities are set to resume classes on Monday.
Video from the scene showed firefighters shooting streams of water at the club and shirtless men trying to break down a wall with axes.
Smoke billowed outside the front of the building as the stench of fire filled the air, said Max Muller, who was riding by on his motorbike when he saw the blaze.
Muller recorded video of a chaotic scene outside the club, which showed emergency crews tending to victims and dazed clubgoers standing in the street. Bodies lay on the ground beside ambulances.
Friends who were inside the club told him that many struggled to find the exits in the dark. Muller, who was not inside the club Sunday morning but has been there twice before, said there were no exit signs over the doors. It is rare to see such signs in Brazilian clubs.
Valderci Oliveira, a state lawmaker, told Band News that he saw piles of bodies in the club's bathroom when he arrived at the scene hours after the blaze. It looked "like a war zone," he said.
Police told Band News that 90% of the victims were found in that part of the club.
The roof collapsed in several parts of the building, trapping many inside, said Fernandes, the reporter from Band News.
For others, escaping was complicated by the fact that guards initially stopped people from leaving, he said, echoing comments from the state fire official.
"Some guards thought at first that it was a fight, a huge fight that happened inside the club and closed the doors so that the people could not leave without paying their bills from the club," Fernandes said.
The deadly fire is sure to shine a spotlight on safety in Brazil, which is set to host the World Cup next year and the Olympics in 2016.
Many wept as they searched for information outside a local gymnasium where bodies were taken for identification later Sunday. Inside, Brazilian President Dilma Rousseff met with family members and friends as they waited on bleachers for word of their loved ones.
Rousseff became teary-eyed as she spoke of the fire to reporters in Chile earlier Sunday. She had been attending a regional summit there, but cut short the trip and returned to Brazil early to deal with the aftermath of the tragedy.
"The Brazilian people are the ones who need me today," she said. "I want to tell the people of Santa Maria in this time of sadness that we are all together."
The fire started around 2 a.m. after the acoustic insulation in the Kiss nightclub caught fire, said Civil Defense Col. Adilomar Silva.
An accordionist who had been performing onstage with a band when the blaze broke out was among the dead, drummer Eliel de Lima told Globo TV.
Police were questioning the club's owner and interviewing witnesses as part of an investigation into what caused the blaze, state-run Agencia Brasil reported.
The club's license had expired in August and had not been renewed, local fire official Moises da Silva Fuchs told Globo TV.
The incident called to mind a 2003 nightclub fire in Rhode Island where pyrotechnics used by the heavy metal band Great White ignited a blaze that killed 100 people.
Pyrotechnics were also involved in a 2004 nightclub fire in Argentina that killed 194 people and a 2009 explosion at a nightclub in Russia that left more than 100 dead.
Shasta Darlington reported from Santa Maria, Brazil. Marilia Brocchetto and Dana Ford reported from Atlanta. CNN's Catherine E. Shoichet, Helena DeMoura and Samira Jafari contributed to this report.