Four people were killed and two others injured when a small U.S.-registered plane involved in anti-drug operations crashed in a rural area in Choco, a province in northwestern Colombia, officials said.

The two injured people, both U.S. citizens, were taken to hospitals in Bogota following Saturday's accident.

Rescue teams recovered two bodies and may continue the search for the other two bodies on Sunday, army 4th Brigade commander Gen. Nicasio Martinez told Caracol Radio.

"Police are working to find the other two bodies, but it's rough terrain and it's making their job even more difficult," Martinez said.

The small plane, which took off from an airport in neighboring Panama, was carrying five American crewmen and a Panamanian officer assigned to anti-drug patrols under the Salas-Becker Agreement.

Panama's naval air service confirmed that a Panamanian was among those killed in the crash.

"The plane was carrying five American crewmen and a Panamanian officer as shiprider. Four (people) were killed, including the Panamanian officer (Lt. Lloyd Nuñez), and two American crewmen survived," the naval air service said. EFE