Tune in to "AC360°" for the latest on the search for quake survivors in Chile and the race to deliver aid. "AC360°," 10 p.m. ET Monday.
Concepcion, Chile (CNN) -- A tale of two Chiles began to emerge late Monday, with life starting to return to normal in Santiago, Chile, and northern parts of the country, while other areas struggled with lack of food and water and looters roaming the streets.
Nearly three days after an 8.8-magnitude earthquake, rescuers in the hardest-hit areas, including the city of Concepcion, Chile, and the Maule and Bio Bio regions, scrambled to reach possible survivors. Looting broke out as thousands of residents in southern and central Chile remained without food, water, electricity, gas and other basic services.
"The situation there is quite precarious," U.S. Ambassador Paul Simons said at an afternoon teleconference from Santiago. He described the damage as "major, major devastation."
More than 700 bodies have been retrieved, and officials say the toll could climb.
Massive swaths of the area were leveled in Saturday's quake, with buildings toppled into ruin and roads made unpassable with gaping fissures. Cars were tossed about like in a children's toy set.
Stores have been looted and one was set on fire Monday in Concepcion, sending thick plumes of black smoke into the afternoon sky. Military officials said a curfew in the city, Chile's second most important and densely populated municipality, would be in effect from 8 p.m. Monday to noon Tuesday.
Looting and vandalism has been reported in the city, and many residents set up roadblocks at neighborhood entrances and patrolled the streets. Many in the ad hoc security committees carried sticks or clubs and some had attached knives to the tips of their weapons.
The military must provide security throughout the town, one woman said in an interview with CNN Chile, CNN's partner network in the nation.
"We don't want to spend one more night in the darkness and in fear," said Jacqueline Van Rysselberge. "We are no longer hungry, we are so scared."
Officials said they were sending more soldiers into Concepcion.
While security was a concern in Concepcion, most of the fatalities occurred in the nearby city of Maule, where 544 of the 723 reported deaths occurred.
In Maule a sewer system collapsed, several water towers were close to toppling and people in many communities lacked basic services, the National Emergency Office said Sunday.
It was a different situation in Santiago, the nation's capital, where electricity and water services were restored to much of the city and many residents could use their cell phones and other conveniences. About 90 percent of the city's stores were open, Simons said.
"Santiago has returned to normal fairly quickly," the ambassador said.
In the quake's immediate aftermath, more than 1.5 million people had been without power in and around Santiago, according to Chile's National Emergency Office.
Rescuers from Santiago, recently returned from a stint in quake-ravaged Haiti, worked through the day to free people who could be trapped in a 15-story building in Concepcion, about 70 miles (112 kilometers) from the earthquake's epicenter.
Fire commander Juan Carlos Subercaseaux confirmed Monday that three people were trapped in the collapsed building, according to CNN Chile. Rescuers said they heard banging and yelling from an apartment, CNN Chile reported.
Authorities believe 40 or 50 people could be inside the building, but do not know whether they are alive. Video on CNN Chile showed a woman's body being removed from the building's seventh floor Monday afternoon.
Six hospitals in Chile collapsed and another two were severely damaged in the earthquake, the World Health Organization said, adding there's a shortage of health care personnel.
The Chilean air force has set up four field hospitals, each holding up to 60 patients. WHO on Monday called on other countries in the region to send field hospitals and generators to help.
The rescue-and-recovery work unfolded as Chile's defense minister blamed the navy for not issuing a tsunami warning after Saturday's earthquake rocked the South American country.
A large wave crashed into the Chilean islands of Juan Fernandez, killing at least eight people and leaving another eight missing, the Chilean emergency office said. Waves also caused damage along the coast of the Chilean mainland.
A warning could have allowed villagers on the coast to flee to higher ground.
"The truth even if it hurts [is that] a division of the navy made a mistake," Defense Minister Francisco Vidal told reporters.
After the quake struck early Saturday morning, President Michelle Bachelet said a tsunami was unlikely.
Dozens of countries posted tsunami warnings, and Chilean authorities later realized the large waves that slammed their country's coastal areas were generated by the earthquake.
"What we saw ... is a tsunami," Vidal said.
The navy has an emergency system under which captains in each port may issue warnings when sea levels begin to rise, even when the navy doesn't issue a warning. Those port captains eventually sounded the alarm, warning residents to flee.
All 300 American and Chilean employees at the U.S. Embassy are safe, Simons said.
There were no reports of any American fatalities or serious injuries, he said, but efforts to locate and contact thousands of Americans living and working in the country continued.
Calling the quake an "unthinkable disaster," Bachelet said a state of catastrophe in the worst-hit regions would continue, allowing for the restoration of order and speedy distribution of aid.
The government hopes to resume normal commercial air service soon, Bachelet said in remarks the Chilean government published on its Web site.
Authorities also were working to prevent the possible spread of disease, she said.
"Earthquakes or tsunamis like those that we have had cause a great quantity of diseases," Bachelet said.
"We're facing an emergency without parallel in the history of Chile. The passage of time has demonstrated that we're facing a catastrophe of unforeseen intensity, one that caused damages that are going to require immense, united efforts from all sectors of the country -- private and public," Bachelet said.
As desperate residents in Concepcion scrounged for water and supplies inside empty and damaged supermarkets Sunday, authorities used tear gas and water cannons to disperse people in some areas.
Bachelet said the government and the country's major supermarkets had reached an agreement under which the stores will give away basic foods to those affected by the quake.
Chile has received offers of international aid and will accept the help that it needs, Bachelet said.
The nation's ambassador to the United States, Jose Goni, listed Chile's top priorities Monday afternoon.
"After a detailed assessment of the situation," Goni said, "the Chilean government has requested aid from the U.S. government consisting essentially of field hospitals, power generators, water-purification plants, rescue teams, medical crews, tents, satellite telephones, temporary infrastructure for people in need and dialysis autonomous systems."
The United Nations said Monday that Chile had requested international assistance and indicated it is ready to help.
U.S. Secretary of State Hillary Clinton will travel to Santiago on Tuesday on a previously scheduled trip through Latin America. She originally was scheduled to arrive Monday.
Saturday's earthquake is tied for the fifth-strongest since 1900, according to the U.S. Geological Survey. Another 8.8 quake struck off the coast of Ecuador in 1906.
Stronger earthquakes occurred in Kamchatka, in northeastern Russia, in 1952 (magnitude 9); off the west coast of northern Sumatra in 2004 (magnitude 9.1); at Prince William Sound, Alaska, in 1964 (magnitude 9.4); and just south of Concepcion, Chile, not far from the epicenter of Saturday's quake, in 1960 (magnitude 9.5).
More than 90 aftershocks have been recorded since Saturday, ranging from 4.9 to 6.9 in magnitude. A 6.2-magnitude aftershock was recorded near the earthquake's epicenter Sunday.
Bachelet said Saturday that about 2 million people had been affected in some way, but she did not elaborate. The Chilean Red Cross reported that about 500,000 homes sustained considerable damage.
President-elect Sebastian Piñera sought to rally spirits in nationally televised remarks Sunday night, announcing a reconstruction plan called "Up With Chile."
"We will raise Chile," Piñera said. "It's not going to be a short task. It's not going to be easy. It will require a lot of effort, a lot of resources, and a lot of time."
CNN's Karl Penhaul, Brian Byrnes, Bertha Ramos-Rodriguez and Andreena Narayan contributed to this report.