Police has said that they have uncovered a mass grave in central Mexico with the remains of 14 or 15 people believed to have been executed by the Zetas drug gang. The remains found in Guanajuato State were so badly burned that officials were not immediately able to identify the number of victims, and it may be difficult to identify the dead. Guanajuato Attorney General Carlos Zamarripa on Wednesday said the 14 or 15 bodies were piled into a single pit discovered on Saturday, a day after a shootout between police and suspected Zetas hit men in the town of Apaseo el Alto. In the shootout, 12 gunmen were killed, 12 were captured and one police officer was wounded, officials said. The dead gunmen were not the bodies in the mass grave. A large cache of weapons, including assault rifles, grenades and bulletproof vests, was also discovered after that clash, Zamarripa said. Investigations into the confrontation led police to the grave site. In the Pacific port city of Manzanillo, customs officials announced yesterday they had seized more than four tons of precursor chemicals commonly used to make Ecstasy. The drugs were found inside an abandoned shipping container that arrived on a ship from Shanghai, China. On Tuesday, authorities announced the discovery of nearly 1,000 pounds (450 kg) of cocaine hidden in a shipment of tires from Colombia in the same port.