A senior U.S. official told CNN a radar system detected a surface-to-air missile system engage and track an aircraft shortly before the flight, carrying 298 people on board, crashed to the ground.
Another radar system detected a heat signature at the same time.
The White House doesn't believe Ukraine had the ability to shoot down the Boeing 777, nor did the country have the motivation, the official said.
Ukrainian officials have blamed pro-Russian separatists for the attack, while Russian President Vladimir Putin said the Ukrainian military was to blame.
"This tragedy would not have happened, if there had been peace on that land, or in any case, if military operations in southeastern Ukraine had not been renewed," Putin said in televised remarks. "And without a doubt the government of the territory on which it happened bears responsibility for this frightening tragedy."