The nine men aboard a U.S.-flagged vessel found to be carrying nearly 400,000 liters (105,674 gallons) of diesel fuel were detained on suspicion of smuggling, the Mexican navy said Thursday.

The possible contraband was spotted Wednesday during a routine inspection of the Captain Kenny in waters of the Gulf of Mexico about 172 kilometers (107 miles) northeast of Dos Bocas, a port in Tabasco state.

The "crew could not justify with documentation or records the existence of 395,342 liters of diesel in (the vessel's) storage and ballast tanks," the navy said in a statement.

Naval units escorted the Captain Kenny to Dos Bocas and handed over the crew and the fuel to prosecutors.

Fuel theft in Mexico rose 38 percent last year compared with 2010, to 6.8 million barrels, according to a report from state-owned Petroleos Mexicanos, and has become a substantial source of revenue for organized crime.

Pemex has filed a lawsuit in U.S. federal court against 14 American firms the Mexican oil giant accuses of knowingly buying stolen fuel from south of the border. EFE