DERNA, Libya (AP) — The wall of water several stories high smashed into apartment buildings, drowning entire families in minutes.

One man, Fadellalah, believes 13 members of his extended family died. He’s yet to hear about the fate of another 20, several days after two dams burst above the Libyan coastal city of Derna, unleashing epic floods that wiped out neighborhoods and sent some of the dead into sea.

Thousands of others like him are frantically trying to find out who survived the rain-swollen rampage.

As a powerful storm bore down on his hometown, Fadellalah, an information technology worker in Libya’s capital of Tripoli, called his family Sunday to urge them to move to higher ground.

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“No one expected this,” said Fadelallah, who asked that his surname not be used because he fears reprisal from government officials and armed groups who could view his story as criticism of their efforts.

“Some of them didn’t have cars. They didn’t have a way to get out,” he said Wednesday of his family.

Torrential rainwater that gushed down steep mountainsides and into the city killed thousands. Those who survived recount nightmarish scenes, with bodies piling up quicker than authorities can count them.

Mediterranean storm Daniel caused deadly flooding in many towns of eastern Libya. But Derna, renowned for its white villas and palm trees, was the worst-hit. The city had no evacuation plans, and residents said the only warning was the explosive sound of the dams rupturing.

Location proved the difference between life and death.

Fadelallah said all 13 deceased members of his family lived in a neighborhood near the river valley. Their bodies were recovered and buried by the Red Crescent, their names inked on a list of the deceased sent to him by the medical group.

Mohammed Derna, a teacher and 34-year-old father of two, said he and his family and neighbors rushed upstairs. Outside he saw people, including women and young children, just being carried away. They spent Sunday night on the roof of their apartment block before managing to get out Monday morning.

“They were screaming, help, help,” he said over the phone from a field hospital in Derna. “It was like a Hollywood horror movie.”

Emad al-Falah, an aid worker from Benghazi who arrived in the city on Wednesday, said search and rescue teams have been combing apartment buildings for bodies and retrieving corpses turned back by the sea. A litany of social media videos and images show similar distressing scenes.

“It’s a complete disaster. Bodies are everywhere, inside houses, in the streets, at sea. Wherever you go, you find dead men, women, and children,” al-Falah said.

The startling devastation has underscored Libya’s vulnerability. The oil-rich country has been divided between rival administrations, each backed by competing armed militias, for almost a decade. It has been rocked by conflict since a NATO-backed Arab Spring uprising toppled autocratic ruler Moammar Gadhafi in 2011.

Search teams combed streets, wrecked buildings and even the sea for bodies in a devastated eastern Libyan city on Wednesday, where authorities said massive flooding had killed at least 5,100 people, with the toll expected to rise further. (Sept. 13)

Both governments, and their various international patrons, have banded together to help those affected. But progress has been slow. Key bridges, roads and other infrastructure are gone. Derna, which had a population of 90,000, largely was cut off from the world before the first aid convoys arrived late Tuesday.

As of Wednesday, at least 30,000 people were displaced by the flooding in Derna, the U.N.’s International Organization for Migration said. Many fled to nearby cities and towns less impacted by the storm.

One of them is Ahlam Yassin, a 30-year-old housewife, who left for the eastern city of Tobruk.

“Everything has gone,” said Yassin, who waded barefoot with her family through knee-deep water to leave her neighborhood. “The city itself has gone.”

Mahmoud al-Baseer’s cousins lived lived less than kilometer -- roughly 0.6 miles -- from one of the dams. They survived, he said, by quickly escaping to the upper floors of their three-story apartment block and were lucky that the structure held its ground.

Al-Baseer, who lives in the United Kingdom, initially feared they had died. Until he reached them Tuesday evening, he struggled to watch the destruction from afar.

“I could not carry on watching those social media videos,” he said.

Fadelallah said his parents have made it to Benghazi, hoping to reunite with relatives from Derna. And he said he hopes to return soon to give his deceased relatives a proper Islamic funeral.

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Jeffery reported from London. Associated Press journalist Samy Magdy in Cairo contributed to this report.