Iran investigators say Ukrainian plane never called for help

The crew of a Ukrainian jetliner that crashed in Iran never made a radio call for help and were trying to turn back for the airport when the plane went down, according to an initial Iranian report released on Thursday on the disaster that killed 176 people.

The report suggested a sudden emergency struck the Boeing 737 operated by the Ukrainian International Airlines early Wednesday morning, when it went down just moments after taking off from Imam Khomeini International Airport in Tehran.

Investigators from Iran's Civil Aviation Organisation offered no immediate explanation for the disaster, however.

Eyewitnesses, including the crew of another passing flight, described seeing the plane engulfed in flames before crashing, the report said. The crash caused a massive explosion when the plane hit the ground, likely because the aircraft had been fully loaded with fuel for the flight to Kyiv, Ukraine.

The report also confirmed that both of the so-called "black boxes" that contain data and cockpit communications from the plane had been recovered, though they had damaged and some parts of their memory was lost.

It also said that investigators have initially ruled out laser or electromagnetic interference as causing the crash.

Ukrainian President Volodymyr Zelenskiy, meanwhile, said crash investigators from his country had arrived in Iran to assist in the probe. He also said he planned to call Iranian President Hassan Rouhani about the crash and the investigation.

"Undoubtedly, the priority for Ukraine is to identify the causes of the plane crash," Zelenskiy said. "We will surely find out the truth."