Bolivian police, transported in U.S. Army helicopters, raided a cocaine laboratory today in remote northeastern Bolivia and arrested a pilot said to be in the process of dismantling the facility, as a planned series of joint U.S.-Bolivian strikes began.

No shots were fired in the attack in which tons of chemicals and a Cessna aircraft were seized, according to the Minister of Information, who announced the action in the capital of La Paz. He said the laboratory was capable of producing up to 3,300 pounds of cocaine a week. The minister, Hernan Antelo, said he did not know if any cocaine had been seized in the raid.

While political opposition and labor leaders protested the involvement of U.S. troops and equipment in the operation, informed sources said the raids would continue at the rate of at least one a day and would probably increase as U.S. and Bolivian teams become accustomed to working together.

The exact location of today's strike was not given, but it was known to be in the Beni region, a vast area of open grassland alternating with dense jungle that provides camouflage for the clandestine facilities and airstrips used by drug traffickers.

Coinciding with the assault on laboratories in the Beni, Bolivia's U.S.-financed special antinarcotics police have stepped up raids on coca paste-manufacturing facilities in the Chapare region, a belt of fertile land at the eastern base of the Andes where much of Bolivia's coca leaf is grown. The information minister told reporters that in the past few days police had seized six coca paste facilities as well as 50 buildings in which coca leaves are stamped by foot to extract the liquid that begins the process of cocaine production.

Sources knowledgeable about the operation said they do not expect the raids to yield many arrests, nor do they anticipate finding much finished cocaine at the sites targeted for attack. The aim of the strikes, the sources said, is mainly to reduce the capability of narcotics traffickers to produce the drug.

It is also known that drug enforcement officials have concrete evidence that some major drug traffickers have fled following premature disclosure earlier this week of the planned raids.

The 160 U.S. personnel participating in the Beni operation, the largest involvement of American military in an overseas antinarcotics project, are deployed at two locations: a forward base on a ranch somewhere in the Beni, and a rear base here in Trinidad on the grounds of a Bolivian Air Force base.

Bolivian newspapers today carried statements from a range of opposition politicians and labor groups denouncing the presence of U.S. soldiers in Bolivia, while at the same time endorsing the need to combat drug trafficking.

The country's largest union, the Bolivian Workers Central, accused the government of putting Bolivia's national sovereignty and security at risk by inviting U.S. personnel to participate in the raids. The union confederation representing Bolivian peasants, many of whom live by cultivating coca leaf, called the American involvement "a disguised invasion."

Legislators objected to the fact that the government had not sought Congress' approval before launching the operation. Government officials have said that the operation does not require congressional approval because it is in compliance with an international convention signed by the United States and Bolivia and because the U.S. military participation is what the government has described as of a "technical character."

This backwater town, which until this week was more concerned with cattle rustlers and flood waters than with cocaine smuggling, has found itself a focus of world attention as the hub of the U.S.-Bolivian operation.

People here welcome the publicity, if it will mean an end to a drug addiction problem that had just begun to menace Trinidad's youth. But they do not like the notoriety created by press reports that have portrayed Trinidad as a world center of cocaine production.

"We're a poor and humble town," said Pedro Alvarez, a merchant who became mayor six months ago. "This is not a drug trafficking town."

The elaborate facilities of chemical vats and generator-powered drying rooms used for processing coca paste into cocaine are outside Trinidad, spreading in all directions across the Beni. There is little sign that the huge profits from the drug trade have filtered into Trinidad, a town of 50,000 where the few roads that are not made of dirt are paved unevenly with yellow bricks.

Officials here said the trafficking in the region goes on above their heads, in the small aircraft that carry tons of coca paste to the private airfields beside the cocaine processing plants and that then ferry finished cocaine from Bolivia to the United States and Europe.

No one seems to ask many questions about who owns the ranches used for cocaine production. The distance between estates is great and means of communication are difficult, affording traffickers the privacy they seek.

Instead of expensive cars and luxury mansions associated with drug money, people in Trinidad tend to travel by motorcycle and live in adobe huts with red clay tile roofs.

Contact with the capital of La Paz, 360 miles to the west, is infrequent. Basic facilities are lacking. To provide drinking water for the U.S. military contingent camped here, local officials had to dig a special well this week.

This year marks the 300th anniversary of the town's founding by Spanish missionaries. But the mayor is still trying to fathom why this site was chosen, since in the rainy season from November to April it is prone to heavy flooding. An earthen dike encircles the town to keep it from disappearing entirely under water. Even so, the sidewalks are raised more than a foot above street level.

The main legitimate business in this region is cattle ranching. About 3 million head of cattle are raised in the Beni, and Trinidad's Federation of Ranchers has 5,000 members. But ranchers are suffering from a shortage of credit and investment capital, which has caused land values to fall in recent years.

"The drug problem makes us look bad internationally," said the rancher federation's acting president David Shriqui. "Narcotics is the greatest scourge of our region."

While trafficking seems to take place away from Trinidad, this town's peace has been disturbed in recent months by growing drug use among youths who smoke cheap cigarettes made from coca paste.