WASHINGTON (AFP) - A US warship intercepted a submersible believed to be linked to the drug trade off Colombias Pacific coastline, Colombian officials said Saturday. The USS Simpson, a guided missile frigate, immobilised the craft and detained four men aboard, the Colombian Navy said in a statement. The move was authorised as part of an agreement interdicting sea crafts transporting drugs signed between Bogota and Washington. The four Colombians aboard the 'narco sub opened the valves when they saw the Simpson and sank their vessel, the statement read, noting that such crafts can transport up to 12 tonnes of cocaine. The Colombian Navy has intercepted, sometimes with help from other countries, 39 submersibles, including six in 2009, thwarting 'the transportation of more than 30 tonnes of cocaine abroad. Security officials report an increase in the use of locally-built submersibles which can be at sea for up to 14 days and have a range of up to 3,200 kilometres.