A plane carrying three Americans crashed Tuesday in southern Colombia while searching for three other Americans captured by rebels last month, the U.S. Embassy said.

Colombian troops reached the crash site near Larandia military base in southern Colombia's Caqueta state, but the fate of the three-man crew was unknown, said U.S. Embassy spokesman Gerald McLoughlin.

The cause of the crash of the Cessna 208 was unknown, McLoughlin said. A Colombian military official, speaking on condition of anonymity, said the plane had been incinerated in the crash and that there appeared to be the burned remains of the three crew members in the wreckage.

The crash happened between 7 and 7:30 p.m., about an hour after sunset, McLoughlin said. Recovery crews were to revisit the crash site after daylight Wednesday.

The three Americans hostages were apparently captured by the Revolutionary Armed Forces of Colombia, or FARC, after their U.S. government plane crashed in rebel territory Feb. 13. They were on an intelligence-gathering mission.

The rebels executed a fourth American and Colombian soldier who were also aboard, Colombia's army chief has said.