Mexico attorney general's office says it has opened an investigation into the spray-painting of pre-Hispanic stone carvings in a cave in central Mexico.

The office says unknown vandals defaced ceremonial carvings of a celestial sky inside a site known as the Devil's Cave in Tlaxcala state.

The site is believed to have been used by shamans for agricultural rituals and is surrounded by hallucinogenic plants used in the ceremonies, said anthropologist Guadalupe Reyes, director of social communication for San Juan Totolac, the town where the damaged petroglyphs were found.

The attorney general said in a statement Tuesday that red spray paint was found on the carvings, violating a federal law protecting monuments and archeological sites.

Tlaxcala is the same state where residents recently tore down an 18th century chapel.