Vandals stole four ancient Indian rock carvings from a heritage site in the Sierra Nevada mountains near Bishop, California, it has been revealed.
The thieves used cement-cutting powersaws to dislodge the petroglyphs from the volcanic rock in which they were carved between 3,500 and 5,000 years ago.
Six carvings were targeted in all, and around a quarter of the remote site was defaced.
One of the ancient etchings was found dropped and smashed in a nearby car park, while another remained in place, but was badly scarred by hammer marks.
Experts suggested that just one of the ancient panels could be worth $1,000 on the black market.
US government archaeologist Greg Haverstock told NBC News that the theft was "the worst act of vandalism ever seen" on the site. He added:
"The individuals who did this were not surgeons, they were smashing and grabbing. I think it's akin to someone going and cutting pieces out of the Wailing Wall,"
The authorities have also informed leaders of the Paiute-Shoshone tribe, which considers the carvings sacred.
"It was the toughest phone call I ever had to make," said field officer Bernadette Lavato, speaking to the Los Angeles Times.
"Their culture and spiritual beliefs had been horribly violated. We will do everything in our power to bring those back."