CAIRO (AP) — Four Greek rescue workers dispatched to Libya following devastating flooding in the eastern city of Derna were killed in a road collision Sunday, Libya’s health minister said.

Some 11,300 people died when two dams collapsed during Mediterranean storm Daniel last week sending a wall of water gushing through the city, according to the Red Crescent aid group. A further 10,000 people are missing, and presumed dead.

Rescue workers from Greece, Turkey, Egypt and other countries have flocked to the decimated port city to offer help.

On Sunday, a bus carrying 19 Greek rescue workers collided with a vehicle carrying five Libyan nationals on the road between the cities of Benghazi and Derna, health minister Othman Abduljaleel said at a news conference. Three Libyans in the oncoming vehicle were also killed.

Seven of the surviving Greek rescue workers were in critical condition, the minister said.

In a parallel statement, the Greek Foreign Ministry acknowledged the crash but said only three of its nationals had died while two others were missing. The Associated Press was not immediately able to reconcile the conflicting reports.

The disaster has brought some rare unity to oil-rich Libya, which has been divided between rival governments in the country’s east and west that are backed by various militia forces and international patrons. Residents from the nearby cities of Benghazi and Tobruk have offered to put up the displaced, while volunteers have helped hunt for survivors buried beneath the rubble.

But the opposing governments have struggled to respond to the crisis. Their recovery efforts have been hampered by confusion, difficulty getting aid to the hardest-hit areas, and the destruction of Derna’s infrastructure, including several bridges.

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

On Saturday, Libya’s general prosecutor, al-Sediq al-Sour, opened an investigation into the collapse of the two dams, built in the 1970s, as well as the allocation of maintenance funds. Derna’s mayor, Abdel-Moneim al-Gaithi, was suspended pending an investigation into the disaster.

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

Haider al-Saeih, head of Libya’s center for combating diseases, said in televised comments Saturday that at least 150 people had suffered from diarrhea after drinking contaminated water in Derna.

To prevent disease outbreak, Abduljaleel said his ministry had began “vaccinations against diseases that usually occur after disasters such as this one.”