MEXICO CITY – Authorities found the remains of at least 23 people in a series of pits and scattered on the ground at a suspected drug-gang dumping site near the industrial hub of Monterrey in northern Mexico, an official said Friday.

Investigators were using heavy equipment to search for more bodies at the rural site outside Mexico’s third-largest city, local media said. Photographs showed charred spots on the soil suggesting some bodies may have been partially burned.

“There are some (bodies) that can be identified, but others are not in good condition and we will have to run DNA tests,” Eduardo Saucedo, director of investigations for Nuevo Leon state prosecutors, told the newspaper Milenio.

Saucedo said officials still had to inspect three more pits for bodies.

The state attorney general’s office in Nuevo Leon state, where Monterrey is located, said more heavy equipment was being brought in to search the ground and pits where the remains were found.

The bodies were too badly decomposed for immediate identification, the office said.

The clandestine grave site, which was discovered Thursday, was believed to have been used by drug gangs that operate in the area.

The Mexican army did not offer any immediate information on how the site was detected.

Nearly 25,000 people have been killed in Mexico since the government launched an offensive against drug cartels in late 2006.

Cartel hit men have been known to use mass dumping sites to dispose of their victims. In late May, police in the central Mexico tourist town of Taxco discovered 55 bodies in an abandoned silver mine.

Speaking at a military academy graduation ceremony Friday, President Felipe Calderon praised the army’s role in the drug fight and called the drug cartels “the greatest threat to the well-being and progress of Mexican families, and the greatest danger to the liberties that our country’s founders gave their lives to obtain for us.”

Calderon said that “our determination is not only not to take a single step backward, but to carry on decisively with this fight, to persevere in the effort until we reach the victory that Mexico deserves.”