The Reagan administration has toughened its drug enforcement by allowing the Coast Guard to seize any boat or ship on which even a small amount of contraband is found, Transportation Secretary Jim Burnley said Saturday.

Since the policy was enacted April 11, the Coast Guard has confiscated nine vessels including a $300,000 yacht off the coast of Florida that would not previously have been seized, officials said.A confiscated boat must be returned to its owners only only if allegations of illegal drugs on board are proved to be false. Otherwise, the boat is turned over to U.S. Customs, which can sell it at an auction.

"This new policy should be taken as fair warning to anyone who is using or transporting any detectable amount of drugs on our waterways, whether it's in a commercial vessel, a row boat or a million-dollar yacht," Burnley said at a news conference.

"They will not only be prosecuted to the fullest extent of applicable state and federal laws, but will be risking the loss of their property as well."

Burnley said the administration now has "zero tolerance" toward illegal drug use. The new policy is an extension of the previous strategy of focusing on larger quantities of drugs where there was an intent to deal, Burnley said.

The tougher policy is an attempt to reduce demand for illegal drugs, Burnley said. He said it is "based on the notion that when we permit even the smallest drug infraction what some still call recreational drug use we open the door a bit wider for drug smugglers around the world and for drug users in this country."

In Florida, ship owners found in possession of small amounts of drugs often haven't been prosecuted because the U.S. attorney's office was flooded with bigger drug cases, said Lt. Cmdr. Jim Simpson, spokesman for the Coast Guard district based in Miami.

"Now we will at least be able to take the boats away," Simpson said. "It should be a deterrent."

On another front in the government's drug crackdown, customs agents at Oroville, Wash., on the Canadian border, reported seizing an $60,000, 18-wheel truck loaded with aluminum Friday after a "roach clip" and cigarette papers were found in the truck's cab.