TEHRAN, Iran — Iranian investigators say the crew of the Ukrainian jetliner that crashed outside Tehran Wednesday never made a radio call for help and were trying to turn back to the airport when the plane went down.
Iran's civil aviation authority made the comments in a preliminary crash report released on Thursday.
The crash of the Ukrainian Boeing 737-800 on Wednesday killed all 176 people on board.
An early report from Iran's semi-official news agency ISNA blamed some kind of engine failure. But Ukrainian officials say it's too early to determine the cause, and Ukraine's embassy in Iran retracted a statement that also attributed the crash to an engine malfunction.
But the 800 version of the jet, also known as a 737 Next Generation or NG, has had its own problems. Boeing has delivered about 6,700 of these jets to airlines around the world.
The Associated Press and CNN contributed to this story