BY JENNIFER BABSON

  KEY WEST - Federal authorities have taken custody of a Cuban man who hijacked a Cuban plane, threatening to blow it up with fake grenades, and demanded to go to the United States. At about 11:34 a.m., the Soviet-made twin-engine AN-24 touched down at Key West International Airport, shadowed by a Black Hawk customs helicopter.

  The alledged hijacker, seven crew members and 25 passengers -- 12 men, nine women and four children -- exited the plane one at a time. One of the first to disembark was the hijacker, whose name has not been released. SWAT team members forced him to the ground and an officer in bomb squad gear removed two objects from his pockets.

  The small black objects shaped like grenades turned out to be ceramic, authorities said.

  Also aboard the plane were the hijacker's wife and 4-year-old son, who clung to his leg as he exited the plane.

  All of the men on board the aircraft -- except for one wearing an airline uniform -- were forced to lay face down in the tarmac with SWAT team guns trained on them. Some of the men lay next to the AN-24, others lay in the shade of the Douglas DC-3 -- parked just 40 feet away -- that was hijacked by six Cuban men and flown to Key West less than two weeks ago.

  More than two dozen police, FBI and immigration officials surrounded the plane, which is identified with the tail number, CU-T1294. The SWAT team entered the plane at about noon, followed by a bomb squad member wearing protective gear.

  The hijacked plane was escorted into United States airspace at 11:34 a.m. by two F-16 fighter jets from the 482nd Fighter Wing at the Homestead Air Reserve Base.

  ''We escorted the plane to the Naval Air Station Key West,'' said Air Froce Reserve spokeswoman Kathy Paine in Homestead.

  The 482nd recently took over responsibility for such interdiction missions from the 125th Fighter Squadron of the Florida Air national Guard.

  FBI Special Agent in charge Hector Pesquera lead a team of SWAT agents and hostage negotiators to Key West, said FBI spokeswoman Judy Orihuela.

  The Cubana Airlines plane was hijacked late Monday on a flight from Cuba's small Isle of Youth to Havana but was forced to land in the capital because it lacked sufficient fuel to make it to the United States, Cuban authorities said.

  Tuesday morning, a group of passengers safely disembarked in Havana after a tense night of negotiations.

  The plane took off from Jose Marti International Airport about 10:45 a.m. EDT, apparently with the hijacker still aboard.

  The plane has a listed range of about 1,500 miles with a full load of fuel, but aircraft in energy-conscious Cuba often fly only with enough fuel necessary for a safe trip to their scheduled destination. Key West is about 100 miles from Havana.

  The plane spent the night on a tarmac at the Havana airport and shortly after daybreak, a tank with a hose was rolled out onto the tarmac and appeared to be refueling the craft.

  The plane for a time was surrounded by several dozen uniformed police officers, and two fire trucks and numerous ambulances were parked nearby.

  Tuesday morning, two separate groups of as many as two dozen passengers, including a woman with a small child in her arms, jumped from the open back hatch of the plane into the arms of emergency workers below and were taken off the runway in buses.

  The exact number of those who left the plane was impossible to determine from several hundred yards away. Cuban authorities originally had reported there were six children among the 46 people on the craft.

  Shortly before the plane took off, two white cars drove onto the tarmac and a man got out of one and handed three large plastic bags filled with unknown contents to someone inside the plane.

  It was not immediately clear what had happened aboard the plane that led to the release of the passengers after the hijacking drama that began almost 12 hours before when a man claiming to be armed with grenades demanded to be flown to Florida.

  It would be extremely difficult for an average citizen to get access to grenades in communist-run Cuba, where such weapons are heavily guarded by the military. It was also unclear how anyone would be able to get a pair of grenades through the heavy security checks at Cuba's airports, especially less than two weeks after a successful hijacking on the same route of a passenger plane to the United States.

  All incoming and outgoing air traffic at Havana's Jose Marti International Airport was suspended during negotiations.

  Cuban authorities were in communication with the FAA and alerted the U.S. agency minutes before the plane took off from Havana, said Major Ed Thomas, a spokesman for the North American Aerospace Defense Command. Cuba and the United States hav no formal diplomatic ties.

  ''There was some interaction with Cuban authorities,'' Thomas said. ``The F-16s intercepted the aircraft as it crossed the 24 parallel, about 35 miles south of Key West.''

  A government statement released early Tuesday said the Soviet-made Cuban Airlines plane was on a regular passenger flight from the Isle of Youth's main city of Nueva Gerona when the pilot reported that the craft was being hijacked to the United States by a man armed with grenades.

  ''The Cuban authorities, for their part, will undertake the maximum effort to find a solution that preserves the safety and lives of passengers and crew members,'' said the statement.

  The statement blamed the hijacking attempt on what Havana says is the lax treatment that six other suspected hijackers received last month after successfully forcing another passenger plane from Cuba to Key West, Florida, at knifepoint.

  The suspects in the earlier successful hijack were charged with conspiracy to seize an aircraft by force and violence and face a minimum of up to 20 years in federal
  prison. They were granted bond, but remain behind bars because they have been unable to come up with the money.

  Cuban authorities were pleased that American officials decided to charge the six but were enraged last week when a federal judge decided to set bond over the objections of prosecutors.

  ''The entire responsibility of what could happen (in the latest hijack attempt) will fall on the government of that country,'' the Cuban statement said of the United States.

  In that earlier hijacking, six crew members and 25 passengers were on a twin-engine Douglas DC-3 on the same route on March 19 when knife-wielding hijackers took control of the plane as it descended toward Havana after a trip from the Isle of Youth. They diverted the plane to Key West.

  Herald reporters Phil Long and Oscar Corral contributed to this report which was also supplemented with information from The Associated Press.