Officials fear the death toll from Haiti's 7.0 earthquake on Jan. 12 could reach into the tens of thousands, the AP reported on Jan. 14.

The first cargo planes with food, water, medical supplies, shelter and sniffer dogs headed to the Western Hemisphere's poorest nation a day after the quake flattened much of the capital of Port-au-Prince.

Among the buildings that collapsed included hospitals, schools and the main prison, as well as shacks in shantytowns and the National Palace. The capital's Roman Catholic archbishop was killed when his office and the main cathedral fell. The head of the U.N. peacekeeping mission was missing in the ruins of the organization's headquarters.

Bodies were everywhere in Port-au-Prince. Haiti's leaders struggled to comprehend the extent of the catastrophe, the worst earthquake to hit the country in 200 years.

"It's incredible," President Rene Preval told CNN. "A lot of houses destroyed, hospitals, schools, personal homes. A lot of people in the street dead. ... I'm still looking to understand the magnitude of the event and how to manage."

Preval said thousands of people were probably killed. Leading Sen. Youri Latortue told The Associated Press that 500,000 could be dead, but conceded that nobody really knows.

"Let's say that it's too early to give a number," Preval said.

In Petionville, next to the capital, people used sledgehammers and their bare hands to dig through a collapsed commercial center, tossing aside mattresses and office supplies. More than a dozen cars were entombed, including a U.N. truck.

Nearby, about 200 survivors, including many children, huddled in a theater parking lot using sheets to rig makeshift tents and shield themselves from the sun.

Looting began almost as quickly as the quake struck at 4:53 p.m. and people were seen carrying food from collapsed buildings. Many lugged what they could salvage and stacked it around them as they slept in streets and parks.

People streamed into the Haitian countryside, which showed little sign of damage. However, ambulances and U.N. trucks raced toward Port-au-Prince.

About 3,000 police and international peacekeepers cleared debris, directed traffic and maintained security in the capital. However, law enforcement was stretched thin.

An American aid worker was trapped for about 10 hours under the rubble of her mission house before she was rescued by her husband, who told CBS' "Early Show" that he drove (160 kilometers) to Port-au-Prince to find her. Frank Thorp said he dug for more than an hour to free his wife, Jillian, and a co-worker, from under about a foot of concrete.

The international Red Cross said a third of the country's 9 million people may need emergency aid, a burden that would test any nation.

President Barack Obama pledged an all-out rescue and humanitarian effort. American officials said they were responding with ships, helicopters, transport planes and a 2,000-member Marine unit, as well as civilian emergency teams from across the U.S.

"We have to be there for them in their hour of need," Obama said.