By SAM DILLON

          MEXICO CITY -- Slipping into a fashionable private art gallery here late last week, thieves
          threatened onlookers with firearms, packed up 12 paintings by Rufino Tamayo, one of the
          country's great masters, and fled. It was the largest single robbery of contemporary Mexican art in
          memory.

          The value of the stolen works, which had been on loan from American and Mexican collectors for an
          exposition celebrating the 100th anniversary of Tamayo's birth, was estimated at $2 million.

          The robbery on Thursday evening came moments before the prestigious Lopez Quiroga gallery in the
          Polanco neighborhood closed, and one day before the exposition was to be dismantled and the
          works returned to their owners.

          Art experts said they believed that the methodical manner in which the thieves gathered and packed
          the canvases, leaving behind dozens of other Tamayo works, suggested that they might have been
          hired by a criminal organization to carry out the heist.

          "There have obviously been many art robberies here, but I can't recall any occasion on which 12
          major works have been stolen at once," Raquel Tibol, one of Mexico's most prominent art critics,
          said in an interview.

          Tamayo, who was born in the southern state of Oaxaca and died in 1991, is considered one of
          Mexico's 20th-century artistic giants.

          Because he outlived Diego Rivera and other major Mexican artists of the century, he achieved
          special renown during his lifetime. He had close friendships with a succession of presidents and other
          members of the Mexican elite.

          "Mr. Tamayo believed in universality," said his 1991 obituary in The New York Times. "Many of his
          paintings have a generic quality. Their slightly schematic, gestural, figurative style, shaped by
          modernist developments like cubism, surrealism and expressionism, can seem so familiar that they
          could have been painted almost anywhere."

          That description applies clearly to all the 12 works stolen last week.

          They were all small oil paintings, each measuring less than 2 feet in either dimension, painted between
          1929 and 1988. They included "Sandias," or Watermelons, a 1965 still life; "El Payaso," or The
          Clown, a 1988 portrait with cubist overtones, and "Abejas Agresivas," or Angry Bees, a 1953
          abstract.

          Tamayo's paintings have fetched above $2 million in New York auctions, usually selling for less than
          comparable works by Diego Rivera and his wife Frida Kahlo, but often for far more than canvas
          paintings by the classic muralists Jose Clemente Orozco and David Alfaro Siqueiros, Ms. Tibol said.

          The 12 paintings were part of an exposition of about 50 Tamayo oils, lithographs and etchings that
          had been on display here since December.

          The Mexico City newspaper La Jornada reported that the missing paintings had all been insured by
          an American company, New Northern Fine Art. Efforts to reach the company, or to confirm its
          name, proved fruitless.

          Thursday's robbery was carried out by five men, dressed casually but well in order to mingle with
          other members of the public at the Tamayo exposition, the gallery owners told local journalists. After
          brandishing their weapons to threaten the gallery staff and a handful of onlookers, the thieves lifted
          the 12 paintings from the walls, wrapped them carefully in plastic bags and packed them in the van in
          which they escaped.

          "The people who entered the gallery to steal the paintings knew very well what they were doing,"
          Mauricio Tornero, the director of Mexico City's detectives, who is in charge of the investigation, told
          Reuters.

          Photographs of the 12 paintings were printed in several Mexican papers, partly at the request of the
          Lopez Quiroga gallery, whose directors said they hoped that publication of the images would help
          reduce their marketability.

          The most costly art thefts in Mexico have been of pre-Colombian works, several experts said. In
          1985, thieves working on Christmas Eve stole 140 of the nation's most prized archaeological
          artifacts, including precious jars and figures fashioned of gold, jade and obsidian, from the National
          Museum of Anthropology.

          Another notorious robbery was the October 1976 theft of 10 works by Mexico's 19th-century
          landscape master Jose Maria Velasco, from the private collection of the Mexican poet and museum
          organizer, Carlos Pellicer Camara. Those paintings, two of which the thieves sliced from their frames
          with a knife, have never been recovered. But Pellicer's nephew said he believed that last week's
          robbery was more sweeping.

          "I've never heard of such an important robbery," the nephew, Carlos Pellicer Lopez, said in an
          interview.

                     Copyright 1999 The New York Times Company