A preliminary investigation indicates that an Indonesian airliner was going more than twice the normal landing speed as it skidded off the runway and burst into flames in central Java last month, killing 21 people. As Chad Bouchard reports from Jakarta, the report has alarmed aviation experts monitoring the case.

Investigators say the Garuda Indonesia Boeing 737 was traveling more than 410 kilometers an hour when it struck the tarmac and careened off the end of the runway into a rice field.

A preliminary report given to the families of the victims reveals there were no mechanical problems before the landing, and the weather was calm. That contradicts the pilot's account that a sudden downdraft caused the crash.

Investigators have not determined a cause of the crash.

Aviation safety analysts say the plane's landing speed as outlined in the report is double the appropriate speed for the short runway at Yogyakarta airport.

Heru Sutono is the coordinator for the Transportation Safety Society in Indonesia.

"Looking at this extremely, much higher landing speed, to my point of view, the only possible cause: a malfunction," he said. "Something is not right. So high a speed can happen only when the flap doesn't retract."

Sutono says he has interviewed passengers from the crash who saw that the wing flaps were not retracted before the landing. He says that could indicate a mechanical malfunction, but also might indicate the pilot was trying to get airborne again in an effort to try landing a second time.

The preliminary report also indicates the runway at Yogyakarta airport is only a quarter the recommended length by international standards.

Aviation experts say short runways are common in domestic airports, but the Garuda plane might have been able to land safely at the reported speed if the runway had been longer.

The report also says that fire engines and rescue vehicles at the airport were not properly equipped.

Indonesian officials say the full report and investigators' findings will be released within a few weeks.