Mexico City - The Mexican Navy intercepted a small submarine with drugs between the southern Mexican states of Oaxaca and Chiapas, on the Pacific, Mexican media reported Thursday.

Navy Commander Jose Maria Ortigon was quoted in the daily El Universal as saying that four Colombians were arrested in the operation Wednesday, in which five boats and two helicopters took part.

The suspects were taken to the port of Huatulco by helicopter.

The load is presumably cocaine, although it was held in sealed compartments within the submarine that had not yet been opened. The authorities expected it to reach Puerto Vallarta early Friday for inspection.

The Mexican Navy said that such submarines can carry up to 10 tonnes of drugs. This transport method was first used in 2006, when three submarines were found with drugs. The boats are built in Russia and were first used to transport drugs by the Revolutionary Armed Forces of Colombia (FARC). (dpa)