Ukraine outlined four potential scenarios on Thursday to explain the deadly crash of one of its airliners in Iran, including a missile strike and terrorism, as Iranian investigators said the plane was on fire before it fell to the ground.

Kiev said its investigators wanted to search the site of Wednesday¡¯s crash southwest of Tehran for possible debris of a Russian-made missile used by Iran¡¯s military. An initial report by Iran¡¯s civil aviation organization said the plane had experienced an unspecified technical problem.

The Ukrainian International Airlines Boeing 737-800, flying to Kyiv and carrying mostly Iranians and Iranian-Canadians, crashed shortly after taking off from Tehran¡¯s Imam Khomeini airport, killing all 176 people on board.