Traces of marijuana, cocaine and "speed" were found in blood and urine samples of the Amtrak switch operator who fled his post after a train derailment last month, officials said yesterday.

Laboratory samples taken from Thomas Connor 3 1/2 days after the accident registered positive for marijuana, cocaine, methamphetamine and amphetamine, more commonly known as speed.

The test results do not measure impairment, and Federal Rail Administration officials said they cannot determine if drug use contributed to the accident.

Arthur Donato, Connor's attorney, told United Press International that Connor told investigators he was not under the influence of alcohol or drugs the night of the accident. "All other evidence involved in this investigation corroborates Mr. Connor's position and there's clearly no reasonable suspicion that drugs or alcohol were involved," Donato said.

Donato did not return telephonecalls from The Washington Post.

Connor has acknowledged to investigators that he neglected to change a switch that would have diverted the Washington-to-Boston Night Owl to a clear track. Instead, the 10-car train plowed into a maintenance vehicle on the track. Twenty-five people were injured and two were hospitalized overnight. The Night Owl's two locomotives derailed, but the other cars remained upright.

Connor, who was immediately suspended without pay by Amtrak, resigned from the railroad the day before a disciplinary hearing was scheduled.

The accident occurred Jan. 29 at 12:32 a.m. near Chester, Pa., almost two miles from the Hook tower, where Connor was working. He told investigators he drove to the scene after hearing about it over his radio, then fled when he saw the wreckage. He resurfaced three days later, on Feb. 1, and met with investigators from the National Transportation Safety Board. He submitted to a drug test about 4 p.m. that day.

Federal rail regulations require railroad employees involved in an accident to submit to drug and alcohol testing within eight hours.

Because of the time lapse, the FRA asked toxicologists to test the specimens to the smallest detectable amount consistent with reliability of the equipment and procedures.

FRA Administrator John H. Riley said the results illustrate the importance of post-accident testing and pointed out that a recent 9th U.S. Circuit Court of Appeals decision, which found that railroad workers cannot be tested unless they show signs of impairment, likely would have prevented testing in this case.