The Bureau of Land Management (BLM) called the carvings sliced out of the rock face with cement-cutting circular saws an "irreplaceable part of our national cultural heritage."
"The damaged site is a pristine example of Great Basin rock art and hunter-gatherer domestic, religious and subsistence activities," said Greg Haverstock, a BLM archeologist based in Bishop, eastern California.
Bernadette Lovato, manager of the BLM field office in Bishop, some 200 miles (320 kilometers) inland from San Francisco, added: "The individuals who did this have destroyed an irreplaceable part of our national cultural heritage.
"We have increased surveillance of our sites and are working with other agencies to bring the responsible parties to justice and to recover the petroglyphs."
The petroglyphs, etched by ancient hunters 3,500 years ago, had survived winds, floods and earthquakes over the centuries but were hauled off in a matter of hours.
A fifth suffered deep saw cuts and a sixth was removed but broken and abandoned near a parking lot in the Eastern Sierra desert, while dozens of others were scarred by hammer blows.
The stolen slabs of rock were two feet (60 centimeters) square, and up to 15 feet off the ground, requiring ladders and electrical generators for the power saws.
The ancient carvings show circles, deer, snakes and hunters with bows and arrows.
The area is known as the Volcanic Tableland, and is considered sacred territory for Native Americans of the Paiute-Shoshone tribe.
The BLM Bishop field office said it was "offering a $1,000 reward for information leading to the arrest/conviction of the responsible individuals who damaged petroglyph panels at a major rock art site."
"The individuals who did this were not surgeons, they were smashing and grabbing," Haverstock told the Los Angeles Times.
"This was the worst act of vandalism ever seen" on the 750,000 acres of public land managed by the Bishop field office, he added.
Lovato informed tribal leaders after the theft was discovered by visitors on October 31.
"It was the toughest telephone call I ever had to make," Lovato said. "Their culture and spiritual beliefs had been horribly violated. We will do everything in our power to bring those pieces back."
Archeologist David Whitley, who helped the site gain a listing on the National Register of Historic Places, said the theft exposed the vulnerability of such treasures and the difficulty of managing them.
"Do we keep them secret in hopes that no one vandalizes them? Or, do we open them to the public?" he asked.