A general from the Republic of Congo has been arrested in France in connection with 350 refugees who went missing in the central African nation in 1999.
A group representing the families of the refugees praised the arrest on Thursday of General Nobert Dabira, calling it "good news".
Marcel Touanga, the head of the group, said the arrest showed the tragedy had not been forgotten.
"We are fighting for the truth in the face of strong forces because there are links between the organisers of these massacres and some French personalities," said Touanga, whose 28-year-old son was among the missing.
Dabira, 64, was accused of torture and kidnapping on a massive scale by examining magistrates after being arrested in the town of Torcy near Paris.
Dabira, who owns a home in France, was released pending trial after he was charged, AFP news agency reported.
The refugees went missing when they returned to the port city of Brazzaville after fleeing from their country's civil war to the neighbouring Democratic Republic of Congo.
Rights groups and relatives say they were tortured and executed upon their return, though Congolese authorities have always denied any massacre.
Dabira is the former inspector-general of the Congolese army, and since October 2012 has been a high commissioner for the re-integration of former soldiers.
When contacted by the AFP, Dabira said he was "totally innocent" and would not leave France during the investigation.
In 2005, Dabira was one of 15 accused - many of them senior army and police officials - acquitted in the case by a criminal court in Brazzaville.
France opened its own inquiry into the alleged massacres in 2002.