Rescuers on Tuesday trawled a muddy river for more bodies and Cambodia prepared for a day of mourning in wake of a stampede by thousands of festival goers which left at least 378 dead and hundreds of injured.

The Prime Minister called it the country's biggest tragedy since the murderous 1970s reign of the Khmer Rouge.

A panic-stricken crowd celebrating the end of the rainy season on an island in a river tried to flee over a narrow bridge in the capital Phnom Penh late Monday and many people were crushed underfoot or fell over its sides into the water. disoriented victims struggled to find an escape hatch through the human mass, pushing their way in every direction.

After the stampede, bodies were stacked upon bodies on the bridge as rescuers swarmed the area.

The search for bodies in and along the Bassac river continued on Tuesday as state television showed horrific footage of twisted and writhing bodies — both alive and dead — piled on each other. some desperately reached out with their hands, screaming for help and grasping for hands of rescuers who struggled to pull limp bodies from the pile as if they were trapped in sand or snow.

It remained unclear what sparked the stampede. police and witnesses pointed to the narrow bridge as providing inadequate access to and from the island. two Singaporean businessmen who organised a sound-and-light show for the festival, said authorities had closed another bridge earlier in the day, forcing tens of thousands of people to use a single span.

One witness said the trouble started when several people fell unconscious in the press of the crowd. another survivor said he heard a police siren just before the panic erupted.

Ambulances raced back and forth between the river and the hospitals for several hours after the stampede. Calmette Hospital, the capital's main medical facility, was filled to capacity with bodies as well as patients, some of whom had to be treated in hallways. relatives, some crying, searched for the missing on Tuesday morning.

"I was taken by shock. I thought I would die on the spot. those who were strong enough escaped, but women and children died," said Chea Srey Lak, a 27-year-old woman who was knocked over by the panicked crowd on the bridge.

She managed to escape but described a woman, about 60 years old, lying next to her who was trampled to death by hundreds of fleeing feet.

"There were cries and calls for help from everywhere, but nobody could help each other. everyone just ran," she said at Calmette Hospital, where she was being treated for leg and hand injuries. Hours after the chaos, the dead and injured werestill being taken away from the scene, while searchers looked for bodies of anyone who might have drowned. hundreds of shoes, water bottles, plastic bracelets and other items were left behind on and around the bridge. one body floated in the river.

A government spokesman, Phay Siphan, said total casualties reached over 1,000 with 378 people killed and 755 injured. but this, he said, was not the final count. authorities said there were no foreigners among the dead or injured.

"This is the biggest tragedy we have experienced in the last 31 years, since the collapse of the Khmer Rouge regime," Prime Minister Hun Sen said, referring to the ultra-communist movement whose radical policies are blamed for the deaths of 1.7 million people during the 1970s.

He ordered an investigation into the cause of the stampede and declared Thursday would be a national day of mourning. government ministries were ordered to fly the flag at half-staff. He said that the government would pay the families of each dead victim 5 million riel ($1,250) for funeral expenses and provide 1 million riel ($250) for each injured person.

City police chief Touch Naroth said on Tuesday that investigators were still trying to determine the cause but suggested that the bridge's small size may have contributed to the tragedy. "This is a lesson for us," he said on state TV.

The Prime Minister's special adviser, Om Yentieng, denied reports that the panic was sparked by people being electrocuted by lighting cables or by a mass food poisoning.

Authorities had estimated that upward of 2 million people would descend on Phnom Penh for the three-day water festival, the Bon Om Touk, which marks the end of the rainy season and whose main attraction is traditional boat races along the river. In 2010 event, 420 of the long, sleek boats competed, with crews of up to 80 racers each.

The last race ended early Monday evening, the last night of the holiday, and the panic started later on Koh Pich Diamond Island a long spit of land wedged in a fork in the river where a concert and exhibition were being held. It was unclear how many people were on the island to celebrate the holiday, though the area appeared to be packed with people, as were the banks.

Soft drink vendor So Cheata said the trouble began when about 10 people fell unconscious in the press of the crowd. she said that set off a panic, which then turned into a stampede, with many people caught underfoot.

Seeking to escape the island, part of the crowd pushed onto the bridge, which also jammed up, with people falling under others and into the water. so Cheata said hundreds of hurt people lay on the ground afterward. many appeared to be unconscious.