TUCSON, Ariz. (AP) _ Federal agents on patrol along the U.S.-Mexican border followed a trail of footprints to a trailer where they arrested three men and confiscated 1 1/2 tons of cocaine, authorities said.

The seizure occurred Monday near Naco, about 100 miles southeast of Tucson, Border Patrol spokeswoman Jacqui Parker said.

Four Border Patrol officers followed footprints to a car and trailer about a quarter-mile north of the border and seven miles west of the crossing at Naco, Chief Patrol Agent Ronald J. Dowdy said.

When the officers saw people carrying bags across the border and loading them into the trailer, they staked out the trailer for two hours before moving in for the arrests, according to Gerald B. Murphy, who is in charge of the Drug Enforcement Adminstration's Tucson operations.

''It's very common for them to stash the drugs somewhere on this side of the border - in a pickup or a camper, or just burying it - and come back to pick it up later,'' Dowdy said.

The agents confiscated 3,192 pounds of cocaine, officials said.

Ms. Parker said investigators did not know where the cocaine came from or for whom the men were working. The case was turned over to DEA officials who said an investigation was continuing, Ms. Parker said.

She said two of the arrested men were carrying assault rifles, while the third had a 9mm semiautomatic pistol.

The suspects were identified as Richard J. Dadd of Sierra Vista, Ariz., and two Mexicans, Javier Gonzales Herrera and Jorge Escalante Gamez, of Cananea, Sonora. A fourth person, described only as a juvenile, was arrested later on charges related to the seizure and released.

The seizure was one of several in southern Arizona in the past week. Other busts netted more than 470 pounds of cocaine and about 4,500 pounds of marijuana and led to arrests of three U.S. citizens, seven Mexicans and one Yugoslavian.