(CNN) -- Three Americans and a Panamanian died when their plane crashed during a mission to monitor drug trafficking in northern Colombia Sunday, U.S. officials said.
Two Americans survived the crash near the city of Capurgana, Colombia, and were rescued by Colombian military forces, according to a statement from the U.S. military's Southern Command. The survivors were taken to a hospital in Bogota, it said.
"There is no indication the plane was shot down," the U.S. military's statement said.
Communications with the DH-8 aircraft, which was contracted by the U.S. government, was lost over the western Caribbean Sea near Panama's border with Colombia, the statement said.
The news release did not identify the Americans or reveal what organization they were working for. The Panamanian who died was a member of Panama's Air National Guard, it said.
The plane's mission was to "provide detection and monitoring of drug trafficking routes in the coastal region of Central America as part of Operation Martillo," it said.
"We express our sympathies to the families of the deceased, and are particularly saddened by the loss of a Panamanian Air National Guardsman," said Gen. John Kelly, commander of the U.S. Southern Command. "We also want to thank the Colombians for their outstanding rescue and recovery efforts."