(Los Angeles Times)

Relief groups and governments struggled today to speed emergency aid to Haiti's earthquake victims, who are increasingly desperate to find food, water and medical help for the many injured.

U.N. officials said today that looters had broken into a warehouse in Haiti's ruined capital, Port-au-Prince, where the World Food Program stored 15,000 tons of food, but they did not know how much of the stockpile was stolen or when the theft took place, the Associated Press reported from Geneva.

U.N. officials warned that residents of impoverished Port-au-Prince are becoming more impatient about the lack of assistance they've gotten since the magnitude 7.0 earthquake devastated their city Tuesday.

The world has vowed its help, but efforts are complicated by earthquake damage to the capital's airport and its seaport, which was closed. Hundreds of U.S. troops were on the ground this morning, the leading edge of a military contingent that is expected to number more than 5,500 by Monday.

"We have much more support on the way," Army Lt. Gen. Ken Keen said on ABC's "Good Morning America," AP reported. "Our priority is getting relief out to needy people, to mitigate the suffering that the Haitian people are experiencing right now."

Former President Clinton, the U.N. special envoy to Haiti, said in a separate television interview that it is crucial to get food and water into Haiti the next four or five days, as survivors are pulled from the rubble by rescue specialists who have begun to arrive in Port-au-Prince.

Clinton said even $10 donations by individuals could make a big difference in coming days. President Obama tapped Clinton and former President George W. Bush to lead fundraising for quake victims.

On Thursday, emergency aid flowed from around the world toward Haiti, only to confront a reality that grew more desperate by the hour: Crippled ports and communications left stunned earthquake survivors on their own to scavenge for food and water, carry away legions of dead and dig frantically for voices calling out from under the rubble.

Obama promised $100 million and the full resources of the U.S. government for what he said would be one of the largest relief efforts in recent history. U.S. officials said 30 countries had either sent aid or promised to do so. Rescue teams from eight countries had arrived.

But two days after the earthquake, there was little evidence of the aid effort in the capital of the hemisphere's poorest country.

"In Haiti, you're lucky if they come with a screwdriver," said Jean Marc Mercier, a Haitian American who spent the last two days hunting for survivors in the wreckage of the Hotel Montana, a longtime gathering spot for diplomats, journalists, humanitarian workers and businessmen.

The toppled six-story hotel was an exception to the scenes of abandonment elsewhere; a rescue team newly arrived from Virginia was combing the debris.

Mercier, who runs a computer business in Haiti, said he and others had been burrowing by hand toward voices calling out from deep inside the wreckage. They had managed to save one woman, an aid worker.

"Last night after I went to bed, all I heard were the voices in my head. One guy told me not to bother: 'Go help people who are in better shape. There is no way you are getting to me,' " said Mercier, 44. "I wasn't able to sleep all night."

Asked how many people were in the hotel when it collapsed, he whispered, "Hundreds."

Aid officials said the risk of violence and looting would increase as scant food and water run out and frustrated families fail to find medical care for the injured.

Officials who were willing to estimate the number of dead acknowledged that they were just guessing. Victor Jackson, an official with Haiti's Red Cross, told Reuters news agency that his organization was estimating 45,000 to 50,000 had died.

All across Port-au-Prince, it seemed, the living bore the dead -- in the beds of pickups, in wheelbarrows, on makeshift stretchers. At a hospital named St. Marie, crowded a day earlier with dozens of people seeking help, the courtyard was empty except for two cleaners mopping bloody water into the street.

Even many who didn't lose their homes were afraid to sleep in them.