JOSHUA TREE NATIONAL PARK, Calif. -

Authorities say they need more time to clean up graffiti that's marred an historic Native American site at Joshua Tree National Park.

Rattlesnake Canyon, a popular hiking spot in the Southern California desert park, was closed for cleanup earlier this year after graffiti was found spray-painted on ancient boulders at 17 sites. Rangers say taggers posted their work online, prompting copycat crimes.

The canyon was supposed to reopen on Tuesday but the Riverside Press-Enterprise says the closure will be extended another 30 days while authorities continue the cleanup along a mile of the canyon.

If caught and convicted, vandals could face up to $5,000 in fines and six months in jail.