The 226 passengers aboard a DC10 jet about to leave Dulles International Airport for Los Angeles were safely evacuated yesterday after a hydraulic leak sent toxic fumes into its cabin.

American Airlines Flight 75 was starting its engines at 5:55 p.m. when fluid leaked from a hydraulic line in the tail onto a hot auxiliary power generator, according to American Airlines spokesman Art Jackson.

Fumes from the flammable, petroleum-based fluid prompted the evacuation down mobile stairways, Jackson said, adding: "I can only assume that the nature of the emergency was not that severe or they would have used the emergency escape chutes."

Five flight attendants were taken to Loudoun County Memorial Hospital in Leesburg where they were released after being examined for possible ill effects from inhaling the fumes.

Jackson said airline personnel have not determined the cause of the leak. The National Transportation Safety Board began an investigation.

The passengers and flight crew left for Los Angeles at 11:15 p.m. aboard a second DC10, which was flown in from Kennedy Airport in New York.

The DC10, one of the mainstays of the airlines, has been dogged by misfortune over the years. Twelve days ago a chartered DC10 crashed in Malaga, Spain, killing 55 people. Investigators said the crash could have been triggered when a tire on its nose wheel failed.