Libya's top prosecutor said he has opened an investigation into the collapse of two dams that caused a devastating flood in a coastal city as rescue teams searched for bodies on Saturday, nearly a week after the deluge killed more than 11,000 people.

Heavy rains caused by Mediterranean storm Daniel caused deadly flooding across eastern Libya last weekend.

The floods overwhelmed two dams, sending a wall of water several metres (yards) high through the centre of Derna, destroying entire neighbourhoods and sweeping people out to sea.

More than 10,000 are missing, according to the Libyan Red Crescent. Six days on, searchers are still digging through mud and hollowed-out buildings, looking for bodies and possible survivors.

Authorities and aid groups have voiced concern about the spread of waterborne diseases and shifting of explosive ordnance from Libya's recent conflicts.

General Prosecutor al-Sediq al-Sour said prosecutors would investigate the collapse of the two dams, which were built in the 1970s, as well as the allocation of maintenance funds.

He said prosecutors would investigate local authorities in the city, as well as previous governments.

“I reassure citizens that whoever made mistakes or negligence, prosecutors will certainly take firm measures, file a criminal case against him and send him to trial,” he told a news conference in Derna late Friday.

It's unclear how such an investigation can be carried out in the North African country, which plunged into chaos after a NATO-backed uprising toppled longtime dictator Moammar Gadhafi in 2011.

For most of the past decade, Libya has been split between rival administrations — one in the east, the other in the west — each backed by powerful militias and international patrons. One result has been the neglect of crucial infrastructure.

Local officials in the city had warned the public about the coming storm and last Saturday ordered residents to evacuate coastal areas in Derna, fearing a surge from the sea.

But there was no warning about the dams, which collapsed early Monday as most residents were asleep in their homes.

A report by a state-run audit agency in 2021 said the two dams had not been maintained despite the allocation of more than $2 million for that purpose in 2012 and 2013.

A Turkish firm was contracted in 2007 to carry out maintainance on the two dams and build another dam in between.

The firm, Arsel Construction Company Limited, said on its website that it completed its work in November 2012. It did not respond to an email seeking further comment.

Local and international rescue teams were meanwhile working around the clock, searching for bodies and potential survivors in the city of 90,000 people.

Al-Sour called on residents who have missing relatives to report to a forensic committee that works on documenting and identifying retrieved bodies.

“We ask citizens to cooperate and quickly proceed to the committee's headquarters so that we can finish the work as quickly as possible,” he said.

Libyan authorities have restricted access to the flooded city to make it easier for searchers to dig through the mud and hollowed-out buildings for the more than 10,000 people still missing.

Many bodies were believed to have been buried under rubble or swept out into the Mediterranean Sea, they said.

The storm hit other areas in eastern Libya, including the towns of Bayda, Susa, Marj and Shahatt. Tens of thousands of people have been displaced in the region and took shelter in schools and other government buildings.

Dozens of foreigners were among those killed, including people who had fled war and unrest elsewhere in the region.

Others had come to Libya to work or were travelling through in hopes of migrating to Europe.

At least 74 men from one village in Egypt perished in the flood, as well as dozens of people who had travelled to Libya from war-torn Syria.