BEIRUT—Weapons experts are inspecting GPS systems recovered from the Sept. 14 missile and drone strike on Saudi Arabian oil facilities for evidence that could reveal their origin and flight path, people familiar with the investigation said.

Officials in Riyadh and Washington have blamed Iran for the attacks and are searching for “smoking gun” evidence. They say they can’t galvanize world support for their view unless they can draw a clear link back to Tehran, which has denied any role in the attacks.

The...