Mexican authorities have discovered at least 250 human skulls in clandestine graves in Mexico's eastern state of Veracruz, authorities told Mexican media Monday.

Veracruz state prosecutor Jorge Winckler told Noticieros Televisa that they were likely to find more.

"There is a part where more than 250 skulls have appeared, in a field where we’ve only made minimal progress," he said in a telephone interview with the broadcaster.

Winckler said that organized crime groups have for many years killed and disposed of people in clandestine graves in Veracruz "with the complacency of the authorities."

"Veracruz is one huge grave," he said.

More than 5,000 people are missing in the state, he said. Authorities have until now found about 150 bodies of people reported missing.

Solecito, a private group searching for bodies, has found more than 200 corpses and more than 60 clandestine graves with human remains, most of which have yet to be identified.

Clandestine graves have also been found in the states of Guerrero, Chihuahua and Morelos, as well as other places in Mexico.

Mexico has for more than a decade struggled with periodic waves of violence tied to organized crime. About 27,000 people were missing in Mexico as of the end of 2015, according to government figures.