The Mexican navy also said they have uncovered a large methamphetamine labaratory, with enough ephedrine to produce more than 40 tonnes of the drug.

The navy said they found 12,905 gallons (49,640 litres) of ephedrine, a chemical used to make methamphetamine, in an enormous tank on top of a mountain in the northern state of Sinaloa

Felipe Calderon, the Mexican president, has sent 45,000 troops and federal police to try to combat powerful smuggling cartels.

But heavily armed traffickers have continued to battle over the lucrative routes, with the violence spreading into the US.

Some 2,750 people have died in drug violence in Mexico this year.