BY FRANCES ROBLES

  BOGOTA -Colombian authorities for the first time Monday night released the names of three Americans kidnapped two months ago when their surveillance plane crashed into the Colombian jungle.

  Keith Stansell, Marco Gonzalves and Thomas R. Howes, civilians doing drug surveillance for the Department of Defense, have been missing since Feb. 13, when their single-engine Cessna crashed here. The plane carrying the three and two others -- American Thomas Janis and a Colombian army sergeant, Luis Alcides Cruz -- reported engine trouble just before it crashed in Caquetá, an area rich with members of the Revolutionary Armed Forces of Colombia.

  The FARC rebel group admits killing Janis and Cruz at the scene, and then taking the three Americans hostage.

  The FARC has waged war here for 40 years in what it calls a quest for social justice. Considered terrorists by the United States government, the 17,000-member group regularly kidnaps either for extortion or to pressure the government.

  The three Americans, the FARC has said, can be exchanged in a broad prisoner swap.

  Both the Colombian and U.S. governments have refused.

  On Monday evening the Colombian attorney general's office announced it had launched an investigation against the FARC's top members, including Manuel Marulanda, Raúl Reyes and Jorge ''Monojojoy'' Briceño Suárez.

  ''They gave the order,'' said a prosecutor who asked not to be named. ``The bosses have to respond to the acts of the men under them.''

  The kidnapping of the three Americans triggered a massive search to find them, involving thousands of soldiers. A second American plane that went to look for them weeks later crashed as well, killing all three aboard.

  The investigation into the top FARC leadership came as Marulanda reached out to the Colombian government, asking for peace talks with military generals. His written overtures Monday puzzled the nation, as President Alvaro Uribe campaigned on the promise to stop negotiations with guerrillas who commit acts of terrorism.

  ''Our job is not to read or receive letters from bandits,'' Colombian Army Gen. Carlos Alberto Ospina said. ``The operations will continue.''