Forensic investigators work at the scene of a Ukrainian plane crash as bodies of victims are collected, in Shahedshahr, Iran. Picture: AP Photo/Ebrahim Noroozi

Dubai – A Ukrainian airliner was on fire immediately before it crashed southwest of Tehran, killing all 176 on board, according to an initial report by Iranian investigators.

The Ukrainian International Airlines Boeing 737-800, flying to Kiev and carrying mostly Iranians and Iranian-Canadians, crashed shortly after taking off on Wednesday from Tehran’s Imam Khomeini airport.

The report by Iran’s civil aviation organisation cited witnesses on the ground and in a passing aircraft flying at high altitude as saying the jet was on fire while still aloft.

The three-year-old jet, which had its last scheduled maintenance on Monday, encountered a technical problem shortly after take-off and started to head toward a nearby airport before it crashed, the report said.

The technical problem was not specified in the report, which also said that there was no radio communication from the pilot and that the aircraft disappeared from radar at 8 000 feet (2 440 m).