Three archaeologists crept over rocky precipes, past dozing rattlesnakes and through sacred rooms deep in the wilds of Arizona to make the first discovery of American Indian catacombs.

The underground chambers, dating back up to 800 years, included tombs and graves, along with massive ceremonial chambers."It's absolutely mind-numbing. We would have never believed it could have existed," John W. Hohmann, one of the archaeologists, said Friday during a meeting of the 2,000-member Society of American Archaeology.

"It will change a lot of what we believed about Indians in the Southwest," he said. "They may have been far more advanced than we believed."

The scientist said he felt a bit like Indiana Jones, the movie archaeologist-treasure hunter, when he lowered himself by rope down steep rock walls into the catacombs.

James Schoenwetter, an anthropology professor at Arizona State University in Tempe, Ariz., said the Indian catacombs are the first reported in the United States.

"The idea of a very elaborate form of ceremonial chamber being built underground hundreds of years ago is surprising," he said.

"For American archaeologists, it's as exciting as finding the tomb of Tutankhamen," said Gabe Decicco, a society spokesman.

The catacombs, explored in August, were made from natural fissures excavated by the Indians about 700 to 800 years ago, Hohmann said.

"The amount of labor that went into it must have been incredible," said Diane E. White, one of the discoverers.

The fissures, at a ancient Indian settlement about two miles west of Springerville, Ariz., near the New Mexico state line, had been noticed before, but never were explored.

"There had been some suspicion that there was something underground there," said archaeologist Christopher D. Adams. "When we actually entered the catacombs though, it just blew us away."

Several hundred graves have been identified, including some under the floors, under stone cairns and in wall tombs. Hohmann said none of the burial sites will be disturbed.

Hohmann expects the site to produce at least one more major find.

"We think there is something else underground there," he said.