Federal authorities said four petroglyphs at least 3,500 years old were cut from rocks in the Eastern Sierra near Bishop known at Volcanic Tableland and were taken away, the Los Angeles Times reported Sunday.
A fifth petroglyph was left defaced by deep saw cuts and a sixth, apparently broken during the theft, was abandoned in the Volcanic Tableland visitor parking lot, the newspaper said.
"The individuals who did this were not surgeons, they were smashing and grabbing," U.S. Bureau of Land Management archaeologist Greg Haverstock said.
"This was the worst act of vandalism ever seen" on the 750,000 acres of public land managed by the BLM field office in Bishop, he said.
Petroglyphs cover hundreds of lava boulders and cliffs in the area with spiritual renderings including deer, rattlesnakes, bighorn sheep and hunters with bows and arrows.
The theft would have taken extraordinary effort, authorities said, as ladders, electric generators and power saws would have to have been driven to the remote and arid high desert site.
While the petroglyphs would not fetch much on the illicit market, experts said -- perhaps $500 to $1,500 -- they are priceless to American Indians who consider them a connection to the souls of their ancestors.