U.S.  media reports say American intelligence officials believe it is likely an Ukrainian passenger jet that crashed shortly after taking off from Tehran was brought down by an Iranian anti-aircraft missile.

Details are still coming in.

"Somebody could have made a mistake on the other side," President Donald Trump said when asked about the crash Thursday, noting the plane was flying in a "pretty rough neighborhood."

Iranian investigators said Thursday the crew of a Ukrainian passenger jet had tried to turn back after takeoff early Wednesday and that the pilot made no radio communications about any problems.

The initial report from iran's Civil Aviation Organization also cited witnesses on the ground and in a passing aircraft as saying the Ukraine International Airlines plane was on fire before it hit the ground.

Ukrainian President Volodymyr Zelenskiy declared Thursday a day of mourning for the 167 passengers and nine crew members who died when the plane bound for Kyiv crashed early Wednesday.

Ukrainian Foreign Minister Vadym Prystaiko said the dead included 82 Iranians and 63 Canadians along with Ukrainians, Swedes, Afghans, Germans and Britons.

Iranian investigators said the voice and data recorders from the Boeing 737 aircraft were been recovered from the crash site, a swathe of farmland on the outskirts of the Iranian capital.

Iran's semi-official Mehr News Agency quoted the head of the nation's civil aviation agency as saying he did not know which country would get the black boxes for analysis, but that Iran would not hand them over to U.S.-based Boeing, the aircraft's manufacturer.

The U.S. National Transportation Safety Board typically participates in investigations of overseas air crashes when a U.S. airline or plane manufacturer is involved. But given the heightened tensions between Washington and Tehran, and the fact that the two sides have no diplomatic relations, it was uncertain whether the NTSB would be involved in the investigation of the UIA crash.

In a statement sent to VOA Ukrainian, the NTSB said it was "monitoring developments surrounding the crash of UIA flight 752" and was "following its standard procedures" for international aviation accident investigations.

"As part of its usual procedures, the NTSB is working with the State Department and other agencies to determine the best course of action," it said.

"The U.S. has not participated in an accident investigation in Iran since Iran's 1979 Islamic Revolution. So it is very unlikely that the NTSB will be involved," said Madhu Unnikrishnan, editor of U.S. airline news service Skift Airline Weekly in a VOA Ukrainian interview.

The jet was built in 2016. It was a Boeing 737-800 model, a commonly used commercial jet with a single-aisle cabin that is flown by airlines throughout the world. It is an older model than the Boeing 737 MAX, which has been grounded for nearly 10 months following two deadly crashes.

Tatiana Vorozhko of VOA's Ukrainian Service and Michael Lipin of VOA Persian contributed to this report.

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