DERNA, Libya (AP) — The United Nations Support Mission in Libya warned Monday that an outbreak of diseases in the country’s northeast, where floods have killed over 11,000 people, could create “a second devastating crisis,” with Libyan authorities reporting the spread of diarrhea among over 100 people who drank contaminated water.

In a statement, the United Nations Support Mission in Libya said it was particularly concerned about water contamination and the lack of sanitation after two dams collapsed during Mediterranean storm Daniel sending a wall of water gushing through the eastern city of Derna on Sept.11. Some 11,300 city residents were killed and a further 10,000 people are missing, presumed dead, the country’s Red Crescent said.

The mission said there are nine U.N. agencies in the country responding to the disaster and working on preventing diseases from taking hold that can cause “a second devastating crisis in the area.” It added the World Health Organization sent 28 tons of medical supplies to the devastated country.

Haider al-Saeih, head of Libya’s Center for Combating Diseases, said in televised comments Saturday that at least 150 people suffered diarrhea after drinking contaminated water in Derna. No further updates have been given.

The disaster has brought some rare unity to oil-rich Libya, which has been divided between rival administrations since 2014. Both are backed by international patrons and armed militias whose influence in the country has ballooned since a NATO-backed Arab Spring uprising toppled autocratic ruler Moammar Gadhafi in 2011.

Residents from the nearby cities of Benghazi and Tobruk have offered to put up the displaced, while volunteers have been looking for survivors buried beneath the rubble.

The opposing governments have both deployed humanitarian teams to the port city and other affected areas country but had initially struggled to respond to the crisis. Their efforts have been hampered by poor coordination, difficulty getting aid to the hardest-hit areas, and the destruction of Derna’s infrastructure, including several bridges.

The Health Minister from Libya’s eastern government, Othman Abduljaleel, said Sunday that his ministry had begun a vaccination program “against diseases that usually occur after disasters such as this one.” He didn’t elaborate further.

As of Sunday, 3,283 bodies had been buried, Abduljaleel said, many in mass graves outside Derna, while others were transferred to nearby towns and cities.

Also Monday, UNESCO said it was concerned about the state of ruins of Cyrene, an ancient Greco-Roman city that lies roughly 37 miles east of Derna.

“UNESCO is in contact with archaeologists on the ground and its satellite imaging team is also trying to establish what the damage might be,” the agency said in a statement sent to the Associated Press.

Cyrene is one of five Libyan UNESCO World Heritage sites.

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Associated Press writers Jack Jeffery and Samy Magdy contributed to this report from London and Cairo respectively.