A Navy helicopter crashed Tuesday off the coast of Colombia and the fate of its crew was unknown, Navy officials said Tuesday.

Cmdr. David Werner, a Navy spokesman who described the incident, said a search and rescue effort was under way.

Another Navy spokesman, Lt. John Schofield, said the helicopter was an SH-60B, which normally operates with a crew of three but can have as many as five. He said it was not yet clear how many were aboard the aircraft. He said it went down under unknown circumstances in international waters west of Colombia.

Colombian officials initially said they had no information about the incident. Adm. Guillermo Barrera, operations chief for the Colombian navy, said there were no reports of a crash in Colombian waters.

Navy aircraft often fly counter-drug missions off ships in the region. Colombia is the world's largest cocaine producer and a major supplier of heroin to the United States.

The U.S. has been helping the Colombian police and military battle the country's drug gangs and have made several major arrests in recent years. The Pacific coast of Colombia, particularly along the edge of coca-growing Narino state, where the land is penetrated by few roads and bisected by inland waterways, is a popular haven for drug smugglers.

Since the year 2000, the United States has spent $4 billion for "Plan Colombia," a joint U.S.-Colombia anti-drug program that ended in September. The United States provides the Colombian government with training, equipment and other aid under the project.