SALT LAKE CITY (AP) – The Bureau of Land Management is looking for vandals who spray-painted targets near ancient American Indian rock art in Utah County.

Investigators found more than a dozen targets on large rocks and outcroppings in the Lake Mountains area west of Utah Lake. The agency says they were painted sometime between July 25 and July 31.

Investigators found evidence of target shooters using large-caliber guns at the site.

Similar vandalism was also found in the area in 2011. The agency says target shooting should be done into soft earth to prevent sparks that can cause wildfires.

The rock art is thought to be several thousand years old. The BLM is offering a $500 reward for information that leads to an arrest.