Baghdad, Iraq ? Saddam Hussein’s government is believed to have buried as many as 300,000 opponents in 263 mass graves that dot the Iraqi landscape, the top human rights official in the U.S.-led civilian administration said Saturday.

Sandy Hodgkinson said the administration had been sending forensic teams to investigate those grave sites reported to U.S. officials. So far, the existence of about 40 graves has been confirmed.

“We have found mass graves with women and children with bullet holes in their heads,” she said.

President Bush has referred to Iraqi mass graves frequently in recent months, saying they provide evidence that the war to drive Saddam from power was justified.

But some human rights activists have criticized the U.S.-led administration in Iraq for moving too slowly to protect grave sites and begin excavations, and have expressed skepticism that it will ever fully identify who is buried in the mass graves.

“There is just no way — technologically, financially — that they’re going to deal with mass graves on this magnitude,” said Susannah Sirkin of Physicians for Human Rights in Boston.

The U.S.-led administration conducted a workshop Saturday to train dozens of Iraqis to find and protect the mass grave sites. Hodgkinson said the workers would be crucial in protecting the sites from desperate relatives trying to dig for evidence of their missing loved ones.

In the weeks after the U.S.-led war drove Saddam from power, relatives damaged some grave sites, using bulldozers that mangled bodies and scattering papers and clothing that could have been used to identify remains.

The largest mass grave discovered so far, a site near the southern town of Mahaweel believed to hold at least 3,115 bodies, was damaged by relatives searching for remains. But officials say most of the mass graves haven’t been disturbed.

Mass graves “tell the story of missing loved ones such as where, when and how they were killed,” Hodgkinson said. “Truth and proper burial is the first step toward reconciliation.”