All 176 people died onboard the Kiev-bound Ukrainian International Airlines Boeing 737-800 when it crashed six minutes after taking off from Tehran on Wednesday. Most of its passengers were Iranians and Iranian-Canadians who were flying the Tehran-Toronto via Kiev route in the absence of direct flights.

Ukraine wants to scour the crash site of its airliner for possible Russian-made missile debris, officials said Thursday as an initial report by Iranian investigators said the plane had been on fire immediately before it crashed.

Ukraine Security Council Secretary Oleksiy Danylov said the country's investigators plan to search for possible Russian missile debris after seeing information about it on the internet.

Russia in 2007 delivered 29 Tor-M1 surface-to-air missile systems to Iran as part of a $700 million contract.

Ukraine is looking at various possible causes of the crash, including a missile attack, a collision, an engine explosion or terrorism, Danylov wrote on social media.

The three-year-old airliner crashed hours after Iran launched missile attacks on U.S.-led forces in Iraq over 1,000 kilometers away, leading some observers to speculate that the plane may have been hit. Tensions between Washington and Tehran have risen with the United States' killing of a top Iranian general Friday and Tehran retaliating with a missile strike on U.S. targets in Iraq.

While Iran did not directly respond to Danylov’s comments, its armed forces spokesman dismissed allegations of a missile strike as “psychological warfare” waged by Iran’s foreign-based opposition, the Associated Press reported.

Iran's civil aviation organization said in its report that the Boeing encountered a technical problem shortly after takeoff and started to head toward a nearby airport before it crashed. Witnesses on the ground and in a passing aircraft flying at high altitude said the plane was on fire while still aloft, the report said.

The technical problem was not specified in the Iranian report, which referred to the crash as an "accident."