A Ukrainian airliner burst into flames shortly after take-off from Tehran on Wednesday, killing all 176 people aboard in a crash that an initial report blamed on engine failure.

Debris and smoldering engine parts were strewn across a field around 10 km (six miles) from Imam Khomeini airport as rescue workers with face masks retrieved bodies of the victims.

Ukraine’s embassy in Iran, citing preliminary information, said the Boeing 737 suffered engine failure and the crash was not caused by “terrorism”.

Carrier Ukraine International Airlines said it was doing everything possible to confirm the cause, and the investigation would also involve Boeing and Ukrainian and Iranian authorities. It was the Kiev-based airline’s first fatal accident.

Ukraine President Volodymyr Zelenskiy said all on board had died. “My sincere condolences to the relatives and friends of all passengers and crew,” he said in a statement.

“The fire is so heavy that we cannot do any rescue ... we have 22 ambulances, four bus ambulances and a helicopter at the site,” Pirhossein Koulivand, head of Iran’s emergency services, told Iranian state television.

Ukraine’s prime minister and Iranian state TV said 167 passengers and nine crew were on board. Iranian TV said 32 of those on board were foreigners.

Ukrainian Foreign Minister Vadym Prystaiko said the victims included 82 from Iran, 63 Canadians, 11 Ukrainians, 10 Swedes, three Germans and three Britons. Most passengers were in transit, the airline said.

Iranian media quoted a local aviation official as saying the pilot did not declare an emergency.

Iranian TV said the crash was due to unspecified technical problems. State broadcaster IRIB said on its website that one of the plane’s two black boxes - the flight data recorder and the cockpit voice recorder - had been found.