Six persons were arrested yesterday and an estimated $20 million in cocaine was seized in a raid on a farmhouse processing lab near Orange, Va., that authorities described as a stop on the international drug trail.

". . . It's a pretty good size cocaine conversion laboratory that's part of an international network," said Bill Schnepper, a spokesman at the federal Drug Enforcement Administration in Washington.

He said the early-morning raid by Virginia state police, Orange County and federal authorities on the farmhouse about 70 miles southwest of the District broke up an element of an operation that spreads over other states.

The street value estimate of the seizure of $20 million was made by Orange County Sheriff William Faulconer.

Those arrested, including the owners of the farmhouse, were being held on charges of manufacturing cocaine or possession of cocaine with intent to sell or distribute, said Orange County Commonwealth's Attorney Chris Honenberger.

"We have field-tested 70 pounds of cocaine," Honenberger said yesterday afternoon. Schnepper said the final tally probably would be about 100 pounds.

Honenberger said more than 1,000 gallons of chemicals used to refine the drug also were found in the farmhouse, which is off U.S. 15 about halfway between Gordonsville and Orange. He estimated the plant could produce 10 to 15 pounds of cocaine in eight hours. CAPTION: Picture, Sheriff's deputy leads suspects from court after raid in which police said they seized $20 million in cocaine.