The pilot of the commuter aircraft that crashed Jan. 19 in Colorado, killing nine people, had cocaine in his body at the time of the accident, federal investigators said yesterday.

The crash may be the first detected drug-related accident in U.S. commercial passenger aviation, officials said.

Laboratory tests found cocaine in the urine of pilot Steven S. Silver, who died at the controls of Continental Express Flight 2286, a twin-engine turbo prop that crashed in snowy mountains a few miles from Durango, Colo., as it approached the LaPlata County Airport, according to a toxicology report released by the National Transportation Safety Board (NTSB).

Safety board spokesman Allan Pollack would not comment on whether the level of cocaine found in Silver's body could have impaired his ability to fly the aircraft.

NTSB investigators have not determined the cause of the crash, which also killed the copilot and seven passengers, and injured eight other passengers, Pollack said.

The tests also found the chemical benzoylecgonine, which is produced by the body as it breaks down cocaine, in Silver's blood and urine, according to the report by the Center for Human Toxicology at the University of Utah.

The results come just two weeks after a call by the Reagan administration for random drug testing of the nation's estimated 500,000 airline pilots, flight attendants, mechanics and other employees.

Transportation Secretary James H. Burnley IV said yesterday in a statement that the toxicology report "is a tragic reminder that not even commercial aviation is exempt from the drug abuse problem which plagues our society and {the report} furthers my commitment toward moving ahead on a comprehensive drug testing regulation for the aircraft industry."

On March 3, when Burnley announced the Transportation Department's proposed rule, it was denounced by the major pilots' and flight attendants' unions as unconstitutional and unnecessary.

The Air Transport Association, which lobbies for the nation's major airlines, indicated tentative support for the proposal, but spokesman Stephen D. Hayes said then, "To our knowledge, there has never been a single major commercial accident attributed to drug use."

A Federal Aviation Administration source said yesterday that marijuana may have contributed to the 1982 crash of a cargo-carrying Learjet in New Jersey.

Drug experts do not agree on whether drug tests can indicate whether an individual is impaired at the time that a urine or blood sample is taken, Burnley acknowledged during a meeting with reporters last week.

The level of cocaine found in the pilot's urine was "very, very high" according to Dr. Don Catlin, chief of the division of clinical pharmacology at the UCLA Medical Center.

Catlin said that, in most such cases, a person would have experienced the effects of the drug within a relatively short time before a blood or urine sample is obtained. But, he said, people react differently and it would be hard to say just how strong an effect the pilot would have felt.

The way a person reacts can be affected by how long he has used the drug, how well his body clears it, and other physiological and psychological factors.

Cocaine byproducts can be detected in the blood and urine up to several days after ingestion, he said. But he cited studies showing that the amount of the drug found in the pilot's body, 0.022 micrograms per milliliter (mcg/ml) in the blood and 1.8 mcg/ml in the urine, suggest use occurred within minutes to four hours before sampling.

Seven survivors of the crash waded through waist-deep snow in darkness to summon help after the 19-seat Fairchild-Swearingen Metroliner III plowed into snow-covered mountains near Boyfield, Colo.

The aircraft was operated under the Continental Express name by Trans Colorado Airlines Inc.

Silver, 36, of Denver, and copilot Ralph Harvey, 42, of Littleton, Colo., were killed. Of the 10 people trapped inside the wreckage when rescuers reached the aircraft, only one survived.

Staff writer Philip J. Hilts contributed to this report.