From a runway strip of hard earth only 700 yards long, a narrow trail leads off into a patch of towering trees where, until last week, a group of about 50 people clandestinely manufactured cocaine hydrochloride in large quantities.

Not visible from the air, the camouflaged laboratory was a self-sufficient encampment of about a dozen huts made of wooden poles and covered with canvas.

Each shack had a special purpose -- one for filtering coca paste, another for purifying it with ether and acetone, a third for drying the drug into cocaine crystals.

There was a kitchen and an outdoor, earthen oven.

Electrical power, mostly to light the rows and rows of bulbs used in the final processing step of drying the cocaine in shallow basins in shacks caked with mud for insulation, came from two giant Brazilian-made generators.

This was the first place a U.S.-Bolivian strike force hit when antidrug raids began last Friday, and it is the operation's only successful seizure so far.

Despite a lack of discoveries, U.S. and Bolivian officials today claimed success in routing the traffickers and disrupting a chain of production that stretched from coca plantations in the Chapare and Yungas regions to processing plants like this one in northeast Bolivia, then on to consumers in the United States and Europe.

Bolivia's major traffickers are reported to have fled the country in recent days to avoid capture, and officials here are doubtful of finding any stashes of cocaine, which they speculate was spirited out of Bolivia in advance of the raid. But they say that the antidrug operation has cost the smugglers millions of dollars and has assured that the traffickers will not be operating in Bolivia at least until the end of the November-to-March rainy season.

"The disappearance of the traffickers is a success in itself, even if they got away," Interior Minister Fernando Barthelemy told a press conference this morning in Trinidad, where the 193rd U.S. Army infantry brigade has set up its rear base camp.

To keep the smugglers away once the United States withdraws its six Black Hawk helicopters and 170 support personnel, Bolivia would like "five or six" helicopters of its own, plus U.S. training and financial support, the minister said.

"We have stopped the traffic," he declared. "For it not to return we will have to maintain a long-term effort."

U.S. Drug Enforcement Administration agents attributed the failure to score hoped-for seizures of cocaine and possibly some significant arrests in the first few days to a combination of outdated intelligence, poor coordination among themselves and the strike force, maintenance problems as well as public disclosure of the operation before it got under way.

No raids were run today or yesterday.

Contrary to statements by Bolivia's minister of information, who had blamed the inactivity on bad weather, DEA officials said the cause was the breakdown of a DC3 airplane used to carry fuel for the helicopters on longer range operations.

The U.S. agents, who asked not to be identified by name, but who included both the DEA station chief in Bolivia and a DEA special agent from Washington, said they planned to run reconnaissance flights ahead of future raids to avoid wasted effort.

They also said that the U.S.-Bolivian operation initially had been scheduled to begin July 4, but the arrival of U.S. aircraft was delayed 10 days due to a strike by the Bolivian petroleum workers union, which temporarily cut off local gas supplies.

Landing at this site four days ago, the American agents said there were indications that the camp's occupants had fled two days before. Chemicals had been dumped hurriedly in the woods and all processed cocaine removed, but the site, empty of workers, otherwise had been left intact.

A Cessna Stationair 8-II landed while the raid was in progress. Its pilot disappeared into the woods, but a 17-year-old, identified as Luis Fernandez, who had come on the plane to help dismantle the camp, was captured and is being questioned.

Meanwhile, Barthelemy said today that police in the city of Santa Cruz over the past few days had arrested 15 persons suspected of narcotics trafficking. Ten other persons targeted for detention have not been found, he said.

Police were in the process today of tearing apart this camp, which was called El Zorro and is located about 150 miles north of Trinidad, near the Mamore River. In the center of a makeshift village, police had piled a number of odd items found here, including cans of automobile oil, large plastic containers for liquids, spools of wire and folded canvas tarpaulins.

In the woods on the edge of the camp clearing stood about a dozen 55-gallon red drums containing ether. Empty bottles of acetone were strewn about, along with torn plastic bags in which cocaine sulfate in paste form had been transported to the site for processing. Rolls of aluminum foil, in which the refined cocaine is wrapped for shipment, also littered the area. A Bolivian police major who briefed reporters, flown to the site in an Israeli-made Araba 201 especially designed for short-distance landing, said that such camps can be set up and dismantled quickly. He and DEA officials estimated that there may as many as 60 or more cocaine processing laboratories here in the Beni, an area covered with grasslands, clumps of forests and a network of rivers and lakes.

U.S. officials said they found ledgers at the camp that may lead them to the owner. Maj. Carlos Vizcarra, deputy commander of the Bolivian antinarcotics police unit in the Beni, said the site probably belonged to Oscar Roca Roca, once a popular singer and now suspected by Bolivian authorities of trafficking. But DEA agents said they were skeptical that Roca owned the camp.

Determining ownership of land plots in the Beni is made difficult, U.S. officials say, by lack of access to title records and by the often chaotic and out-of-date state of the files.

In addition to targeting laboratories, the U.S.-Bolivian operation is going after what officials refer to as "trans-shipment or storage areas," places where cocaine is hidden until clandestine flights ferry the drug out of Bolivia. These sites often are located in thatched-roof Indian villages that dot the region, DEA agents say.

Two of the five targets hit so far were suspected storage areas but turned out to be empty of narcotics. The most recent raid against a presumed lab was on Sunday -- a day the government earlier had said that no operations were tried.

That raid also came up empty-handed, and the DEA agent in charge of the operation said today that the strike force apparently had gone to the wrong coordinate.

"I don't think they went to the place I told them to go," said the U.S. agent, who has been stationed in Bolivia for two years. He noted that air navigation in the Beni is complicated by poor aeronautical charts. Even the best maps, he said, are "off their grid coordinates by 20 to 100 miles in some parts."