Federal officials are investigating the possibility that a form of cocaine use involving fire caused the New Year's Eve plane crash in Texas that killed rock-and-roll star Rick Nelson and six other people, sources said yesterday.

Both the pilot and the copilot, who survived the crash, have told investigators that they attempted to land the plane after a fire started in the passenger cabin.

"He made a good landing," one source said. "Except for the fire, everyone would have survived." The cause of the fire is undetermined.

The sources said that preliminary toxicology reports indicate that Nelson's body contained a measurable level of unmetabolized cocaine, which means the drug had not been absorbed into the system at the time of death. They stressed, however, that final written reports from two toxicology laboratories are pending.

One form of cocaine use, called free-basing, requires mixing cocaine with flammable ether or ammonia. After the chemicals evaporate, the "free-base" cocaine is usually smoked in a glass pipe held over a steady flame, often a cigarette lighter. Users say the drug provides a powerful "high," similar to the one received from injecting cocaine into the veins with a needle.

One of the theories investigators are probing is that a free-base fire ignited the cabin.

Propellants from aerosol cans are sometimes used to aid the free-basing process, and investigators found 18 aerosol cans in the wreckage, although most were in the baggage area. "That could be one can of hair spray and one can of deodorant for everyone on board," a source said. "We just don't know."

The presence of the aerosol cans prompted questions from reporters the day after the crash about the possibility of free-basing, according to investigators.

No clearly identifiable drug paraphernalia were found, the sources said.

Court records in California cite cocaine use by Nelson as an issue in his 1981 divorce, sources said.

Preliminary toxicology reports show that neither the pilot nor the copilot of Nelson's plane had alcohol or drugs in his bloodstream, the sources said. Similar reports are pending on the other passengers who died with Nelson -- five members of his band and his fiance.

The plane was a World War II-era Douglas DC3 and was carrying Nelson and his band from Guntersville, Ala., to a New Year's Eve concert in Dallas.

A broken fuel line was suspected early in the investigation as a source of the fire, but it was established later that the line broke on impact with the ground; the fire clearly started in the air. On-board fire extinguishers in the heating system that should have triggered if a fire started there did not.

The official coroner's report shows "smoke inhalation and thermal burns" as the cause of death, according to Alfred Welch, a Dallas County justice of the peace who signed the report.

Entertainer Richard Pryor suffered severe injuries in 1980 after a flammable drug mixture apparently exploded in his face, badly burning the upper half of his body.