KIEV (Reuters) - Ukraine’s President Volodymyr Zelenskiy said the government was considering several possible causes of a plane crash in Iran, which killed 176 citizens of 7 countries.

FILE PHOTO: Rescue team carries a body at the site where the Ukraine International Airlines plane crashed after take-off from Iran's Imam Khomeini airport, on the outskirts of Tehran, Iran January 8, 2020. Nazanin Tabatabaee/WANA (West Asia News Agency) via REUTERS

The Ukraine International Airline jet crashed shortly after takeoff from Tehran on Wednesday. Among the victims were 82 Iranians, 63 Canadians, 11 Ukrainians, 10 Swedes, three Germans and three Britons.

In a television statement Zelenskiy asked people to refrain from manipulation, speculation, conspiracy theories and hasty evaluations regarding Iran plane crash. He also declared Jan. 9 a day of national mourning.

Zelenskiy, who on Wednesday ended a visit to Oman, laid flowers at the airport of Boryspil, where the crashed plane was based.

“Undoubtedly, the priority for Ukraine is to identify the causes of the plane crash. We will surely find out the truth. For this purpose, a thorough and independent investigation will be conducted in accordance with international law,” Zelenskiy said.

He said that he would speak by telephone with the Iranian president to step up cooperation in investigating the crash.

The cause of the disaster is still unknown. Ukraine’s embassy in Iran on Wednesday dropped an initial reference to engine failure as the cause of the crash.

It said in a second statement that the causes had not been disclosed and that any previous comments were not official.

Iranian investigators said on Thursday that the airliner was on fire immediately before crashing.

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