A fire in a Loudoun County farm-house led to the arrest yesterday of three occupants on charges of manufacturing the hallucinogenic drug PCP, authorities reported.

The arrests came a day after Montgomery County police announced the apprehension of 14 persons involved in a PCP operation in the Rockville area. The Loudoun operation was described by Joseph Milano, special agent for the Drug Enforcement Administration in charge of the Washington area, as an "offshoot" of the Montgomery one.

The Loudoun arrests came after authorities responded to a fire. The fire began, Milano said, when a batch of PCP exploded during the drying process of manufacture. The chemicals used in PCP are extremely volatile when they are being dried.

"There's no fire here, we don't need anybody," one of the occupants of the house said when firemen arrived late Tuesday night, according to Chief Charles Wallace of the Arcola Volunteer Department.

"you've got a lot of smoke," Wallace recalled saying. "Where's the fire?"

"It's upstairs," was the reply, Wallace said.

But, according to the chief, the fire was in the basement of the home located in the Ashburn area north of Dulles Airport. Wallace said one of the residents claimed the fire began when a cooking stove exploded while being prepared for a camping trip.

"This didn't make sense," Wallace said. "There wasn't enough fuel to cause that kind of explosion." He said overhead floor joists were blackened by the explosion.

Fire officials called police, and the Drug Enforcement Administration. The DEA had been monitoring the farmhouse for a month, officials said.

Arrested were John P. Autry, his son, Michael Autry, and Darryl Hocter. Arrest reports listed Autry as born in 1925, his son, who said he was unemployed, in 1955 and Hocter in 1953. Hocter said he is employed as a motorcycle repairman.

Each was released on $10,000 bond after an appearance before U.S. Magistrate W. Harris Grimsley in U.S. District Court in Alexandria. They were ordered to appear for a preliminary hearing on the federal offense July 6,

"I'm here because I'm the guy who leased the place," the elder Autry, who described himself as a retired Army master sergeant, told a reporter. "I didn't know what was going on there."

The fire, authorities said, was reported by one of the occupants who had to borrow a phone at a neighboring house.

PCP (its official name is phencyclidine) is commonly known as "angel dust" or "killer weed" by users, who inhale it or smoke it with marijuana. Easy but dangerous to make, PCP can lead to paranoia, numbness, schizophrenic symptoms and violent outbursts, medical authorities say. Such effects have been reported weeks after the drug was used.