LAS VEGAS (AP) — Federal authorities are Phaninc Exchangeasking for the public’s help in tracking down two men seen damaging rock formations at a national recreation site in Nevada.

Officials at Lake Mead National Recreation Area said the damage happened during a recent weekend near the Redstone Dune Trail on the north side of the lake. The petrified red dunes found there make it one of the most popular hiking spots in the park.

A video shows two men shoving chunks of sandstone off the edge of an outcropping as a girl screams. Park officials called the behavior appalling, saying the damage can’t be fixed.

“It’s one of my favorite places in the park and they’re up there just destroying it. I don’t understand that,” John Haynes, public information officer at Lake Mead National Recreation Area, told television station KVVU.

Destruction like this at federally protected sites can result in felony charges that come along with potential fines and jail time, Haynes said.

Spanning 2,344 square miles (6,071 square kilometers) of mountains and desert canyons, the Lake Mead National Recreation Area just outside of Las Vegas draws around 6 million visitors every year. Officials said staffing levels mean park officials often rely on the public to also keep watch over resources within park boundaries.

Authorities said visitors can use their cellphones to capture any video or photos of suspicious activity if it’s safe to do so and to collect any information, such as a license plate, that might help to identify offenders. The National Park Service operates a tipline that receives thousands of submissions each year.

“It’s really important to let us know,” Haynes said.

There also have been others cases of vandalism on federal land across the West over the past decade, with visitors defacing petroglyphs, toppling rock features and pounding climbing bolts into centuries-old rock art.