Police have uncovered at least 14 bodies in a hidden grave after receiving an anonymous tip in the Mexican resort-town of Acapulco.

The suspected gunmen are still at large. The incident is another blow to a renowned beach resort where drug cartel violence has been on the rise in recent years.

Police uncovered the mass grave after first finding two bodies with drug messages attached to them. Authorities say they received an anonymous call stating the bodies were those of Mexican tourists who were kidnapped last month.

US border police have also found a sophisticated drug smugglers' tunnel linking southern California with Mexico and arrested two people.

The US Customs and Border Protection agency said the tunnel ran between warehouses in southern California and Tijuana, Mexico. It measured 1,800 feet and was equipped with a rail system, lighting and ventilation.

Agents recovered more than 25 metric tons of marijuana in seizures related to the investigation in both California and Mexico and arrested a US citizen and his Mexican wife.