GENEVA (AP) — The downing of Malaysia Airlines Flight 17 may be a war crime, U.N. High Commissioner for Human Rights Navi Pillay said Monday.

Pillay, the U.N.’s top human rights official, called for a thorough investigation into the violation of international law that occurred when the flight was shot down with a surface-to-air missile over a part of eastern Ukraine controlled by pro-Russian separatists on July 17, killing all 298 people on board.