MEXICO CITY (AP) _ Two college dropouts with links to drug dealers and with an obsession for archaeology pulled off the robbery of 124 priceless artifacts from the National Museum of Anthropology in 1985, officials said Monday.

Attorney General Enrique Alvarez del Castillo said the pair visited the museum more than 50 times, made sketches and plans, then jumped the fence, crawled in through an air-conditioning duct and looted seven display cases before dawn on Christmas Day 1985.

Federal police recovered 111 of the artifacts and arrested one of the purported thieves and six associates Friday.

Officials said investigators were stumped for more than three years because they thought professionals were responsible.

''It turned out they were amateurs, two university dropouts who became obsessed first with having and later with selling the archaeological artifacts,'' a source at the attorney general's office said, on condition of anonymity.

Suspects include an American man and an Argentine woman, Alvarez told a news conference, where the artifacts were exhibited on a long table covered with green felt.

''Fortunately, the most significant pieces were recovered as you can see for yourselves. We can place no value on them; they are priceless,'' said Roberto Garcia Moll, director of the National Institute for History and Anthropology, which supervises the museum.

One major piece, a Zapotec mask of the bat god Murcielago from the Monte Alban ruins in southern Mexico, had come apart and had to be repaired, he said.

Alvarez said Carlos Perches Trevino, 24, and Ramon Sardina Garcia carefully staked out the museum. On Christmas Day they jumped the fence of the poorly guarded building in Mexico City's Chapultepec Park and crawled through an air- conditioning duct into the Maya Room, he said.

According to Alvarez, the pair filled a canvas bag with 124 jade, gold and stone artifacts and drove off in a car they left parked outside.

He said they hid the treasure for more than an year, then took it to Acapulco, the resort on the Pacific coast, where they met drug traffickers and tried to interest one, identified as Salvador Gutierrez, in buying the artifacts.

Perches and Sardina traded Gutierrez several artifacts for an unspecified amount of cocaine but never made a deal for the entire cache, Alvarez said.

He said ''the sum of $1 billion was apparently mentioned'' but no deal materialized.

Gutierrez was arrested on trafficking charges this year in Reynosa, across the border from McAllen, Texas, and mentioned the artifacts while under police questioning, Alvarez said.

Federal agents tailed Perches, who had returned to Mexico City with the artifacts, for 45 days before the arrests last Friday.

Alvarez said investigators initially thought 140 pieces were stolen, but later determined the number to be 124.

The artifacts are to be returned to the museum Wednesday at a ceremony attended by President Carlos Salinas de Gortari.

Alvarez said Perches is being charged with theft and damage to national treasures - charges that could mean 10 years in prison upon conviction - and an arrest warrant was issued for Sardina.

Cocaine trafficking and possession charges were filed against Perches; his brother Luis; a U.S. citizen named Gary Nathan Chafee and an exotic dancer and restaurant owner named Isabel Camila Maciero, who performed under the name of The Princess Yamal. Those charges carry a penalty of up to 25 years.

Chafee and two friends of Perches, Juan Castillo Carriles and Hugo Ricardo Perez Radilla, are being charged with cover-up.

Alvarez said an Argentine woman identified as Cristina Gloria Gonzalez was marginally involved and would be deported.

A U.S. Embassy source, who insisted on anonymity, described Chafee only as a ''longtime resident of Mexico City.''