The SH-60B Seahawk helicopter was within visual range of the frigate USS DeWert when it went down in the eastern Pacific, said Bill Austin, a spokesman for the U.S. Naval Station at Mayport, Florida.
"The helicopter didn't transmit any kind of distress call that we know of," Austin said. "There were three crew members on board, and the helicopter was conducting scheduled flight operations."
He said he did not know how far the helicopter was from the ship when it went down, or whether it had just taken off or was returning.
The Colombian navy sent a marine patrol plane to join the U.S. Navy's search, said Adm. Jairo Pena, commander of Colombia's Pacific fleet.
"We received the report that it fell to the water inexplicably," Pena said, adding that the accident occurred about 5 a.m. and Colombian units joined the search by about 8:30 a.m.
He said the U.S. frigate is part of a unit that usually carries out anti-drug missions in international waters. "We are searching in a zone about 350 nautical miles from the Colombian coast," off the port of Buenaventura, Pena said.
"This helicopter that fell had a basic crew on board — the pilot, the co-pilot and a flight technician," he said.
The crew members were assigned to the Helicopter Anti-Submarine Squadron Light 48 based in Mayport, the U.S. Navy said in a statement, but it was unclear what it was doing there.
Navy aircraft often fly counter-drug missions off ships in the area. Colombia is the world's largest cocaine producer and a major supplier of heroin to the United States.
The SH-60B Seahawk involved in Tuesday's crash is manufactured by U.S.-based Sikorsky Aircraft and has a maximum cruising speed of 155 mph. The Navy says the model can carry a crew of up to five and often is used for missions departing from the decks of destroyers and frigates to search for boats or submarines.
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 is a popular haven for drug smugglers, with the lands penetrated by few roads and bisected by inland waterways.
Drug traffickers in this area typically pack several tons of cocaine onto speed boats sometimes equipped with global positioning systems and satellite telephones, and then dart toward Mexico and Central America, where the drugs are taken across land to the United States.
The boats have been known to have custom-made 800-horsepower fiberglass boats that can go up to 50 mph.
Since the year 2000, the United States has spent $4 billion for "Plan Colombia," a joint U.S.-Colombia anti-drug program. The United States has provided the Colombian government with military training, equipment and other aid under the project.
U.S.-made helicopter crashes in Colombia generally have involved U.S.-donated helicopters flown by Colombian troops on military missions. Since 1999, six U.S.-made Black Hawks have crashed in Colombia, killing at least 67 Colombian soldiers and injuring 37.