The United Nations said on Thursday it had information that Libyan guards shot at refugees and migrants trying to flee from airstrikes that killed at least 53 people, including six children, in a migrant detention centre late on Tuesday.

A U.N. humanitarian report said there were two airstrikes, one hitting an unoccupied garage and one hitting a hangar containing around 120 refugees and migrants.

“There are reports that following the first impact, some refugees and migrants were fired upon by guards as they tried to escape,” the U.N. report said.

There are still about 500 people at the detention centre at Tajoura, east of Tripoli, with four Nigerians set for release to the Nigerian embassy on Thursday and a plan for 31 women and children to be sent to the U.N. refugee agency’s departures facility in Tripoli.

Libya is one of the main departure points for African migrants fleeing poverty and war to reach Italy by boat, but many are intercepted at sea and brought back by the Libyan coast guard, with the approval of the European Union.

The 53 dead was the highest publicly reported toll from an air strike or shelling since eastern forces under Khalifa Haftar launched a ground and aerial offensive three months ago to take Tripoli, the base of Libya’s internationally-recognised government in the northwest of the country.