As Haitians waited for aid from other countries, they frantically used whatever was available to save those injured in this week's earthquake.
They used sledgehammers and their bare hands to try to find victims in the rubble. In Petionville, next to the capital, people dug through a collapsed shopping 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 in 90-degree heat.
The global relief effort picked up steam Thursday with a British flight carrying a government assessment team and 71 rescue specialists along with heavy equipment arrived in the neighboring Dominican Republic. The crew prepared to head to Haiti. A Los Angeles County Fire Department 72-member search team left for Haiti late Wednesday.
The United Nations released $10 million from its emergency funds, even as U.N. forces in Haiti struggled with their own losses. The U.N. headquarters building collapsed, and at least 16 personnel are confirmed dead, with up to 150 still missing, including mission head Hedi Annabi of Tunisia and his chief deputy, Luis Carlos da Costa.
"We'll be using whatever roads are passable to get aid to Port-au-Prince, and if possible we'll bring helicopters in," said Emilia Casella, a spokeswoman for the U.N. food agency in Geneva.
Planes carrying teams from China, France and Spain landed at Port-au-Prince's airport with searchers and tons of food, medicine and other supplies — with more promised from around the globe.
Search and rescue squads from Virginia and Iceland arrived Wednesday and some groups — from Cuba's government and Doctors Without Borders — used staff already in the country to offer aid immediately after Tuesday's magnitude-7 quake.
U.S. Secretary of State Hillary Clinton said that "tens of thousands, we fear, are dead" and said United States and the world must do everything possible to help Haiti surmount its "cycle of hope and despair."
The death toll could be between 45,000 and 50,000, with a further three million people hurt or homeless, Reuters quoted a senior Haitian Red Cross official on Thursday.
"No one knows with precision, no one can confirm a figure. Our organization thinks between 45,000 and 50,000 people have died. We also think there are 3 million people affected throughout the country, either injured or homeless," Reuters quoted Victor Jackson, an assistant national coordinator with Haiti's Red Cross.
The U.S. and other nations said they were sending food, water, medical supplies to assist the Western Hemisphere's poorest nation, where a third of the population may need emergency relief.
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In the streets of the capital, survivors set up camps amid piles of salvaged goods, including food being scavenged from the rubble.
"This is much worse than a hurricane," said Jimitre Coquillon, a doctor's assistant working at a makeshift triage center set up in a hotel parking lot. "There's no water. There's nothing. Thirsty people are going to die."
If there were any organized efforts to distribute food or water, they were not visible Wednesday.
The aid group Doctors Without Borders treated wounded at two hospitals that withstood the quake and set up tent clinics elsewhere to replace its damaged facilities. Cuba, which already had hundreds of doctors in Haiti, treated injured in field hospitals.
President Barack Obama promised an all-out rescue and humanitarian effort including the military and civilian emergency teams from across the U.S. The aircraft carrier USS Carl Vinson was expected to arrive off the coast Thursday and the Navy said the amphibious assault ship USS Bataan had been ordered to sail as soon as possible with a 2,000-member Marine unit.
"We have to be there for them in their hour of need," Obama said.
Underscoring deep ties between the two nations, Obama pressed staff to work to deliver relief to Haiti as quickly as possible.
A U.S. military assessment team was the first to arrive Wednesday, to determine Haiti's needs.
Police officers carried the injured in their pickup trucks. Wisnel Occilus, a 24-year-old student, was wedged between two other survivors in a truck bed headed to a police station. He was in an English class when the magnitude-7 quake struck at 4:53 p.m. and the building collapsed.
"The professor is dead. Some of the students are dead, too," said Occilus, who suspected he had several broken bones. "Everything hurts."
Other survivors carried injured to hospitals in wheelbarrows and on stretchers fashioned from doors.
Bodies lay everywhere in Port-au-Prince: tiny children next to schools, women in rubble-strewn streets with stunned expressions frozen on their faces, men hidden beneath plastic tarps and cotton sheets.
Balancing suitcases and belongings on their heads, people streamed on foot into the Haitian countryside, where wooden and cinderblock shacks showed little sign of damage. Ambulances and U.N. 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. The U.N.'s 9,000-member peacekeeping force sent patrols across the capital's streets while securing the airport, port and main buildings.
Calls from victims seeking help from emergency services weren't getting through because systems that connect different phone networks were not working, said officials from a telecommunications provider in Haiti.
Calls were being placed sometimes 15 to 20 times from the same phone, which was "painful to watch," said Jyoti Mahurkar-Thombre, Alcatel-Lucent's general manager of wireless voice.
Looting began immediately after the quake, with people seen carrying food from collapsed buildings. Inmates were reported to have escaped from the damaged main prison in Port au Prince, said Elisabeth Byrs, a U.N. humanitarian spokeswoman in Geneva.
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, said the Rev. Pierre Le Beller at Miot's order, the Saint Jacques Missionary Center in Landivisiau, France.
Haitian Senate President Kelly Bastien was rescued from the collapsed Parliament building and taken to a hospital in the neighboring Dominican Republic. The president of Haiti's Citibank was also among the survivors being treated there, said Rafael Sanchez Espanol, director of the Homs Hospital in Santiago.
The International Committee of the Red Cross said Thursday it has launched a Web site to help Haitians find loved ones missing in the quake.
Robert Zimmerman, deputy head of the group's tracing unit, said people in Haiti and abroad can use the site to register the names of missing relatives.
The Associated Press contributed to this report.