A senior Iranian aviation official was reportedly quoted on state media on Wednesday as saying the black box recovered from a Ukrainian Boeing 737-800 plane that crashed outside Tehran would not be turned over to the U.S. or Boeing.

Reuters reported that Ali Abedzadeh, head of Iran's civil aviation authority, also told Iranian news agency Mehr that it is unclear which country Tehran would send the flight data recording device to for analysis.

His statement comes after officials said 176 passengers and crew members were killed when the Ukraine International Airlines flight bound for Kyiv crashed shortly after takeoff. Authorities are blaming a mechanical issue for the crash.

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It occurred amid missile attacks fired by Iranian forces at Iraqi military bases housing U.S. troops Tuesday evening in response to the U.S. killing of a top Iranian official, Qassem Soleimani. Iranian residents told The Associated Press that they initially feared U.S. retaliation for the crash.

Investigators and aircraft manufacturers often use black box recordings to determine the causes of deadly aircraft incidents, as the devices are designed to withstand the aircraft's destruction and record the last minutes of doomed flights.

A spokesperson for Iran's transportation ministry was quoted by the AP as saying a fire in one of the plane's engines caused the pilot to lose control of the aircraft.

“It was one of the best planes we had, with an amazing, reliable crew,” Ukraine International Airlines President Yevhen Dykhne said of the flight and its crew Wednesday at a press conference.