The takeoff warning system of the Delta jet that crashed at Dallas-Fort Worth International Airport last month worked perfectly in extensive tests, a newspaper reported Saturday.

The wiring, horn and other warning systems parts removed from the wreckage of Delta Flight 1141 were tested this week by The Boeing Co. in Seattle, but the tests did not turn up evidence of a malfunction, sources told the Fort Worth Star-Telegram.The results raise more questions than they answer about what caused the Boeing 727, with 108 people aboard, to crash on takeoff Aug. 31.

"Little by little, we're learning what didn't cause this crash, but we've yet to get a handle on what did," said one federal investigator who was not identified.