The uproar was touched off by a CNN report from Tripoli, Libya, last week, including what was described as surreptitiously recorded video of 12 African migrants auctioned at an undisclosed location there. CNN said it had shared the video with authorities in Libya, and that they had promised to investigate.

Over the weekend, hundreds of protesters demonstrated in front of the Libyan Embassy in central Paris, chanting “Put an end to the slavery and concentration camps in Libya!” and “Free our brothers!” Police dispersed them with tear-gas after the rally turned violent.

The African Union Commission issued a statement after the rally, calling the reported auctions “despicable.” It urged the African Commission on Human and Peoples’ Rights to assist the Libyan authorities with the investigation.

Libya is a major crossroads for tens of thousands of Africans seeking ways to reach Europe, often through unscrupulous smugglers. Thousands of people have fled or been trafficked from Libya in the perilous routes across the Mediterranean Sea for Europe, and many have drowned at sea, including 26 women and girls from Nigeria this month.