In a secret operation with the code name Stopgap, agents of the Drug Enforcement Administration this year used information provided by Navy satellites to track and seize 40 ocean-going vessels attempting to smuggle more than a million pounds of marijuana into the United States.

"Stopgap is one of the most successful operations we've ever had in stopping the flow of narcotics into the U.S.," DEA Administrator Peter B. Bensinger said in an interview yesterday. "Since Stopgap got under way, the price of marjuana in Colombia [the source of the seized drugs] has gone from $20 a pound to as much as $80.

Bensinger said the Colombian price escalated so rapidly because Stopgap cut off the flow of marijuana to the United States by at least one-third. He said that Stopgap resulted in the seizure of "one out of two or three" marijuana shipments from Colombia, which Bensigner said supplies more than half the marijuana coming into the United States. The 1,150,000 pounds of marijuana seized by Stopgap has a retail value of more than $400 million.

Before being boarded and seized by Coast Guard ships operating out of Miami, the 40 vessels Bensinger cited were tracked through clouds and at night by Navy satellites carrying radar that can peer down at the world's oceans in any weather. The satellites are called Navy Ocean Surveillance Satellites (NOSS) and were put into orbit two years ago.

The satellite data on the whereabouts of the marijuana ships was fed into computers at the Naval Ocean Surveillance Information Center (NOSIC), which relayed the information to the DEA. The DEA then informed the Coast Guard, which used some of its largest cutters to intercept the ships before they reached U.S. waters.

Bensinger declined comment on how DEA used the satellite data. The Navy also declined comment on what kind of satellite data it is giving DEA except to say: "The Navy uses all the resources it has."

Operation Stopgap began last December and ended in April, covering the 4 1/2 months that represent the big harvests and shipment of marijuana out of Colombia. Of the 40 ships seized by the Coast Guard during Stopgap, three were carrying more than 150 of the 600 tons of captured marijuana.

The DEA said that the first ship seized under Stopgap was the Night Train, boarded last December. On board were 54 tons of marijuana on the decks of the ship that DEA agents and Coast Guard sailors could almost track the ship by its odor.

Sources said the satellites were no help in spotting or tracking the marijuana on board the ships. The marijuana ships were identified by undercover agents in Colombia. The ships were then tracked by the satellites once they had reached the high seas.

The 40 seized vessels were all what the DEA called "mother ships," ocean-going ships longer than 80 feet that Bensinger said carry the marijuana north to prearranged points 200 miles off the U.S. coast for transfer to fishing boats and small yachts. The mairjuana is then shipped to American ports.

DEA has made 220 arrests as a result of its 40 seizures, almost all of them Colombian nationals. Only the crew of the Night Train was charged with violation of U.S. law. All the others instead were kept overnight in U.S. hotels, then deported to Colombia boarded and seized the Night Train 50 miles east of the Bahams after undercover DEA agents in small boats disguised their identities and bought some of the marijuana being off-loaded from the Night Train on the high seas.

"Except for the Night Train, where we had proof the marijuana was for sale in the U.S., we've been unable to prosecute any of the crews," Bensinger said. "When we asked the other crews if the marijuana was for sale in the U.S. they always said it was bound for the Canary Islands.

In addition to the 40 seized ships, Operation Stopgap encountered four other vessels suspected of carrying marijuana that were scuttled by their crews before the Coast Guard could board them. The crews all took to their lifeboats and were rescued by the pursuing Coast Guard.

"They just pulled the seacocks (water intake valves)," Bensinger said, "and let the ships sink."

Bensinger said that several of the ships the Coast Guard boarded were missing their captians and first officers by the time of boarding. He said that apparently the ships' masters noticed they were being watched and slipped away in small boats at opportune times.

"The crews said they were grateful we found them." Bensinger recalled with amusement. "They said they had been running short of fuel, food and water."

The DEA was able to seize the 40 marijuana ships outside U.S. waters because of arrangements between the State Department and the countries whose flags the ships flew. Bensinger identified these countries as Colombia, Mexico, Venezuela, Honduras, Panama and Liberia.

"We'd identify the ship and then notify the State Department," Bensinger related. "Then the State Department would notify the individual nation, which in all 40 cases gave us permission to board and seize."