PORT-AU-PRINCE, Haiti - Dazed survivors wandered past dead bodies in rubble-strewn streets Wednesday, crying for loved ones, and rescuers searched collapsed buildings as officials feared the death toll from Haiti's devastating earthquake could reach into the tens of thousands.
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 magnitude-7 quake flattened much of the capital of two million people.
Tuesday's earthquake brought down buildings great and small - from shacks in shantytowns to President Rene Preval's gleaming white National Palace, where a dome tilted ominously above the manicured grounds.
Hospitals, schools and the main prison collapsed. 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 multistory headquarters.
At a triage centre improvised in a hotel parking lot, people with cuts, broken bones and crushed ribs moaned under tent-like covers fashioned from bloody sheets.
"I can't take it any more. My back hurts too much," said Alex Georges, 28, who was still waiting for treatment a day after the school he was in collapsed and killed 11 classmates. A body lay a few feet away.
"This is much worse than a hurricane," said doctors' assistant Jimitre Coquillon. "There's no water. There's nothing. Thirsty people are going to die."
Bodies were everywhere in Port-au-Prince: those of tiny children adjacent to schools, women in the rubble-strewn streets with stunned expressions frozen on their faces, men hidden beneath plastic tarps and cotton sheets.
Haiti's leaders struggled to comprehend the extent of the catastrophe - the worst earthquake to hit the country in 200 years - even as aftershocks still reverberated.
"It's incredible," 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.
The lack of communications also frustrated efforts to determine the fate of some 6,000 Canadians living in Haiti, including two missing RCMP officers and former Liberal MP Serge Marcil.
The only known Canadian casualty was a nurse from Elmira, Ont., who died in a building collapse.
Haiti seems especially prone to catastrophe - from natural disasters like hurricanes, storms, floods and mudslides to crushing poverty, unstable governments, poor building standards and low literacy rates.
In Petionville, next to the capital, people used sledgehammers and their bare hands to dig through a collapsed commercial centre, tossing aside mattresses and office supplies. More than a dozen cars were entombed, including a UN truck.
Nearby, about 200 survivors, including many children, huddled in a theatre 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, where wooden and cinderblock shacks showed little sign of damage. Many balanced suitcases and other belongings on their heads. Ambulances and UN trucks raced in the opposite direction, toward Port-au-Prince.
About 3,000 police and international peacekeepers cleared debris, directed traffic and maintained security in the capital. But law enforcement was stretched thin even before the quake and would be ill-equipped to deal with major unrest.
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 kilometres 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 nine million people may need emergency aid, a burden that would test any nation and a crushing catastrophe for impoverished Haiti.
President Barack Obama promised an all-out rescue and humanitarian effort and 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.
The U.S. Navy aircraft carrier, USS Carl Vinson, was expected to arrive off the coast of Haiti on Thursday. More U.S. Navy ships were under way as well, the U.S. Southern Command said.
Canada is also sending helicopters, ships and a disaster response team to rescue those buried alive in the rubble and help thousands of homeless wandering the streets without food, water or medical help.
A huge C-17 military transport plane is scheduled to fly to Haiti on Thursday carrying a utility helicopter and other equipment and personnel. Defence Minister Peter MacKay said the transport planes can be used to evacuate Canadians if necessary.
Naval officials said two ships, HMCS Athabaskan and HMCS Halifax, are being prepared to leave Thursday for Haiti. They will carry everything from a helicopter to chainsaws, generators, and first-aid kits.
Cuba, which already had hundreds of doctors in Haiti, treated the injured in field hospitals. The aid group Doctors Without Borders helped quake victims in tent clinics set up to replace its damaged facilities.
Port-au-Prince's ruined buildings fell on both the poor and the prominent: The body of Archbishop Joseph Serge Miot, 63, was found in the ruins of his office, according to the Rev. Pierre Le Beller at Miot's order, the Saint Jacques Missionary Center in Landivisiau, France.
Senate President Kelly Bastien was among those trapped alive inside the Parliament building, and a day later had stopped responding to rescuers' cries, Latortue said.
Even the main prison in the capital fell down, "and there are reports of escaped inmates," UN humanitarian spokeswoman Elisabeth Byrs said in Geneva.
Haiti's quake refugees likely will face an increased risk of dengue fever, malaria and measles - problems that plagued the impoverished country before, said Kimberley Shoaf, associate director of the UCLA Center for Public Health and Disasters.
Some of the biggest immediate health threats include respiratory disease from inhaling dust from collapsed buildings and diarrhea from drinking contaminated water.
She said swamped clinics may not be able to give people help they need for broken bones and other injuries, leading to complications - a warning borne out on the streets where people, some covered in the dust of collapsed buildings, nursed wounds that bled through crude bandages.
The UN's 9,000-member peacekeeping force sent patrols across the capital's streets while securing the airport, port and main buildings - but also struggled to rescue colleagues from their collapsed headquarters.
The UN Secretary-General Ban Ki-moon announced 16 UN personnel were confirmed dead late Wednesday, with 100 to 150 UN workers still unaccounted for, including the mission chief and his deputy.
He said that 11 Brazilian peacekeepers and five international police officers - three from Jordan and one each from Chad and Argentina - were killed in the "horrendous" quake.
UN officials said 56 others were injured. Seven who were seriously hurt were evacuated from the country, they said.
The U.S. Embassy had no confirmed reports of deaths among the estimated 40,000-45,000 Americans who live in Haiti, but many were struggling to find a way out of the country.
-With files from The Canadian Press.