The US has reportedly identified locations in Iran from which drones and cruise missiles were launched against the Saudi oil facilities on Saturday.
Senior officials told CBS News that the locations were in southern Iran, at the northern end of the Gulf.
Saudi air defences did not stop the drones and missiles because they were pointed southwards, to prevent attacks from Yemen, the officials added.
Iran denies involvement in the attacks, which disrupted global oil supplies.
Yemen’s Iran-aligned Houthi rebels have said they launched the drones that struck the Abqaiq oil processing plant, the world’s largest, and the Khurais oilfield.
They have attacked Saudi oil facilities before, but US officials said on Sunday that they believed the drones and missiles did not originate from the south or south-west, and instead were launched from the north or north-west.