Civilian and military authorities are conducting a search across a wide swath of western Mexico for a navy helicopter carrying four people that disappeared late last week, the Navy Secretariat said Tuesday.

The search for the chopper, which went missing on Friday, is "permanent," navy spokesmen told Efe.

Search teams are looking for the aircraft between Manzanillo, a city in Colima state, and Morelia, the capital of Michoacan state, an area where federal security forces have engaged drug traffickers, mainly La Familia Michoacana and Los Caballeros Templarios, in shootouts in recent years.

The Panther helicopter was flying to Minatitlan, a city in the eastern state of Veracruz, after taking part in a mission in the Pacific region, the secretariat said in a statement.

Panther helicopters are used for "surveillance, transportation, exploration, search and rescue operations" by the navy, the secretariat said.

"As of now, different naval air units are taking part in the search, coordinating with civilian and military authorities," the secretariat said.

"It is not known exactly where" the aircraft disappeared, the navy said, adding that anyone with information about the helicopter should contact authorities.

The navy and army have spearheaded the war that President Felipe Calderon declared on Mexico's drug cartels shortly after taking office in December 2006. EFE