DAKAR, Senegal (AP) — U.N. investigators say crimes against humanity may have been committed when at least 535 people were killed in intercommunal violence over three days in Congo in December.

The investigative team believes the death toll from the massacre in western Congo is likely higher, saying many victims' bodies are believed to have been thrown in a nearby river.

Investigators say the violence between the Banunu and Batende communities began after a dispute over a burial for a Banunu customary chief.

The new report says the attacks "followed strikingly similar patterns and were characterized by extreme violence and speed, leaving little time for people to escape."

The investigation found Banunu villagers were targeted with weapons including firearms and gasoline.