Hundreds of African migrants escaped from a detention center in Tripoli on Tuesday as fighting between rival groups raged nearby, an aid official said, though the Libyan government department set up to combat illegal migration denied the report.

A video posted on social media on Tuesday purportedly showed hundreds of Africans, some carrying plastic bags, walking in a long line away from the detention center. It is located on the road to the former Tripoli International Airport, which was destroyed in a battle between rival militias in 2014.

Libya is a major departure point in North Africa for migrants crossing the Mediterranean Sea to Europe, mainly from other parts of Africa.