Iran says arrests have been made in the downing of Ukrainian International Airlines flight 752.

The attack killed all 176 people on board, including 57 Canadians.

The plane was shot down just hours after Iran launched ballistic missiles at two military bases in Iraq where U.S. forces were being housed.

According to The Canadian Press, a judiciary spokesman for Iran says “extensive investigations have taken place and some individuals are arrested.” They did not say how many people have been detained.

Iran’s President Hassan Rouhani said his government is accountable for the downed plane and said it “must not happen again.” Rouhani called for a special court to be set up to try those responsible for the plane shootdown.

Canadian investigators had their first chance to visit the crash site outside of Tehran Monday.

Canada is part of an international team looking into the circumstances surrounding the incident.