U.S. authorities reportedly suspect that a Boeing 737 that crashed in Iran on Wednesday was likely shot down by Iranian missiles.

CNN on Thursday quoted a U.S. official familiar with intelligence on the incident as saying that the Ukrainian International Airlines jet was downed by two Russian-made surface-to-air missiles.

The U.S. reportedly saw Iranian radar signals lock on to the aircraft before it went down.

The report said the working theory is based on continuing analysis of satellite, radar and electronic data collected routinely by U.S. military and intelligence.

Reuters and other media outlets have reported that Canadian Prime Minister Justin Trudeau and British Prime Minister Boris Johnson have cited intelligence indicating Iran mistakenly shot down the airliner.

The Kiev-bound flight from Tehran crashed hours after Iran fired missiles at U.S. soldiers stationed in Iraq. All 176 people on board were killed, including 63 Canadians.

Iran denies that it shot down the passenger jet, citing technical failure as the cause of the crash.