US officials, according to multiple reports, believe that Ukrainian International Airlines Flight 752 was shot down by an Iranian surface-to-air missile.

The Ukrainian International Airlines plane crashed Wednesday soon after takeoff from Tehran’s airport, killing all 176 people on board.

U.S. intelligence picked up signals of a radar being turned on, sources told Report Focus News. U.S. satellites also detected two surface-to-air missile launches, which happened shortly before the plane exploded, Report Focus News was told.

President Donald Trump said Thursday that he does not believe that the passenger jet went down as a result of a mechanical error, according to CNBC.

Oleksiy Danylov, the secretary of Ukraine’s National Security and Defense Council, wrote on Facebook Thursday that Ukrainian investigators are considering a number of possibilities, including that the plane may have been shot down.

Images showing apparent fragments of a Tor M-1 missile said to have been found outside of Tehran have been circulating on social media

Other possibilities Ukrainian investigators are looking at include an engine explosion due to a technical malfunction, a terrorist attack, or a collision with an unmanned aerial vehicle.