Five rock carvings that were sheared off and stolen from a sacred American Indian site in California's Sierra Nevada have been recovered but no arrests have been made, authorities said Thursday.

Authorities wouldn't provide details about the discovery, only that it was made this month after they received an anonymous tip in a letter. The tipster will be eligible for a $9,000 reward if the information leads to the arrest and conviction of the culprits.

Native Americans carved pictures of hunters, deer and other animals, along with geometric and other designs into a half-mile-long volcanic escarpment. The images, which date back more than 3,500 years ago, adorn hundreds of lava boulders.

It's unclear what will happen to the carvings but federal authorities will be speaking to Paiute-Shoshone tribal leaders to accommodate their wishes.

"This was a terrible thing to happen from their perspective, said David Christy, a spokesman for the Bureau of Land Management. "We are extremely pleased to get them back."

Visitors to the area, known as Volcanic Tableland, discovered the theft and reported it to federal authorities in October. The thieves are believed to have used ladders, electric generators and power saws to remove the panels that are two feet high and wide.

The petroglyphs are probably worth between $500 and $1,500 on the illegal art market but are priceless to American Indians.

Removing or damaging petroglyphs is a felony and first-time offenders can be imprisoned for up to a year and fined as much as $20,000, authorities said.

The site, north of Bishop, is protected under the Archaeological Resources Protection Act and listed in the National Register of Historic Places.