The United States is reinforcing its assessment that Iran was behind an offensive on Saudi oil facilities in September.
New evidence and an analysis of weapons debris from the States indicate that the strike likely came from the north.
In an interim report of its investigation -- seen by Reuters ahead of a presentation on Thursday to the United Nations Security Council -- Washington assessed that before hitting its targets, one of the drones traversed a location approximately 124 miles to the northwest of the attack site.
However, the report noted that the weapons analysis did not definitely reveal the origin of the strike, that initially knocked out half of Saudi Arabia's oil production.
The United States, European powers and Saudi Arabia blamed the attack on Iran.
Yemen's Houthi group claimed responsibility for the attacks, and Iran, which supports the Houthis, denied any involvement.
Yemen is south of Saudi Arabia.