Officials have warned that a disease outbreak in Libya’s northeast, where floods have killed thousands, could create “a second devastating crisis” as adults and children fell ill from contaminated water.

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 Storm Daniel, sending a wall of water gushing through the eastern city of Derna on September 11.

The death toll has varied, with government officials and aid agencies giving tallies ranging from about 4,000 to 11,000 dead.

Haider al-Saeih, head of Libya’s Centre for Combating Diseases, said at least 150 people, 55 of them children, suffered diarrhoea after drinking contaminated water in Derna.

The disaster has brought some rare unity to oil-rich Libya, which has been divided between rival administrations since 2014.

The opposing governments have both deployed humanitarian teams to the port city and other affected areas, but poor coordination, difficulty getting aid to the hardest-hit areas and the destruction of Derna’s infrastructure, including several bridges, have hampered their efforts.