MEXICO CITY – The top prosecutor in Mexico’s Gulf coast state of Veracruz confirmed Tuesday that more than 250 skulls have been found in what appears to be a drug cartel mass burial ground on the outskirts of the city of Veracruz.

State Prosecutor Jorge Winckler said the clandestine burial pits appear to contain the victims of drug cartels killed years ago.

“For many years, the drug cartels disappeared people and the authorities were complacent,” Winckler said, in apparent reference to the administration of fugitive former Gov. Javier Duarte and his predecessors.

In an interview with the Televisa network, Winckler did not specify when the skulls were found or by whom.

But victims’ advocacy groups like Colectivo Solecito have excavated and pressed authorities to excavate such sites for years to find missing loved ones.

Winckler said excavations have covered only a third of the lot where the skulls were found, and more people may be buried there.

“I cannot imagine how many more people are illegally buried there,” Winckler said.

“Veracruz is an enormous mass grave,” he said.

The state had long been dominated by the ferocious Zetas cartel. But the Jalisco New Generation cartel began moving in around 2011, sparking bloody turf battles.

The victims’ advocacy groups have criticized authorities for doing little to try to find or identify the state’s missing people, many of whom were kidnapped and never heard from again.