A mass grave discovered in southern Mexico with the remains of 167 people is approximately 1,300 years old, the Chiapas state prosecutor\'s office said in a statement, after authorities had originally thought the grave was only 50 years old. Forensic experts and anthropologists said the skulls showed signs of artificial deformation practiced more than 1,000 years ago by natives in the area, the statement dated Saturday said. Ancient pottery was also found at the site, it said. The Maya people, who lived in Southern Mexico and Guatemala, would use planks to flatten and elongate the skulls of infants. The grave was discovered in a cave on a remote ranch near the town of Frontera Comalapa, about 11 miles from the Guatemalan border. Authorities said on Saturday that the grave appeared to be at least 50 years old. The top Chiapas official from Mexico\'s national anthropology institute said the site shared characteristics with other cemeteries that date from the years 700 to 1200, the statement said.