WASHINGTON, USA (CMC) – US officials have confirmed they are flying unmanned aircraft, or drones, above the Caribbean Basin in search of narcotics cargo.

Department of Homeland Security officials said other surveillance technology, including radar-equipped P-3 aircraft, last up to only 10 hours – not long enough to pinpoint drug runners on the high seas. They said the drones can loiter in the skies twice as long.

They said part-submarine vessels travelling great distances without surfacing to refuel are emerging as a key vehicle for ferrying drugs through the Caribbean Sea.

And cocaine-laden speedboats often sail at night to evade capture, the US officials added.

“The goal is to be on station long enough to detect and track targets making their way through the transit zone and bring in units for the intercept [that] can track a variety of smuggling vessels, including semisubmersibles and go-fast vessels,” said Lothar Eckardt, executive director of DHS Customs and Border Protection national air security operations.

“It doesn’t matter what the target is; it matters that we are able to stay out and look for it,” he added.

Eckardt said the Guardian, a maritime version of Homeland Security’s other Predator drones, is mounted with search radar and an electro-optical/infrared sensor.

Since 2011, US officials said the Miami-based Joint Interagency Task Force South, a command with staff from DHS and the intelligence community, as well as the US Defence and Justice departments, has disrupted five semisubmersibles, each escorting more than 6.5 tonnes of cocaine.

Of the 214 reported incidents, the stealth vessels evaded authorities 79 per cent of the time, the Department said.