A painstaking cleanup has removed the paint that vandals splattered on petroglyphs in northern Arizona but also left behind what may be a permanent mark on the rock where the etchings sat undisturbed for at least 1,000 years.

The paint damage was discovered on a wall of petroglyphs in a box canyon called Keyhole Sink near Williams. The Kaibab National Forest hired a conservator to help repair the panel and the work was completed over two recent days.

The paint was heated with a torch and then soaked up with sponges and paper, said Kaibab archaeologist Neil Weintraub. He said paint residue was lightened with solvent.

Weintraub said workers were pleased to get the big splotch of paint removed so people could see the markings again. But he also said there's now a light spot on the rock where the paint was removed and it's probably permanent, depending on how the rock weathers.

"It will unfortunately never be the same," he said. "There's always going to be an area where you can tell there was paint there."

The Forest Service closed roads leading to Keyhole several years ago to reduce the potential for such damage. The roads were replaced with a trail to the site and signs were put up telling people not to damage the walls, decorated with primitive etchings of animals, a blazing sun and other figures.

The signs were ignored.

In August, Kaibab officials found that someone had painted the word "ace" in thick silver paint above an indecipherable splotch of paint that might also be letters.

Investigators are still trying to find out who did it.

The Kaibab has stepped up patrols of the site by its staff and volunteers. It's against federal law to deface the petroglyphs and violators can face fines, prison or both.

Weintraub estimated it cost $3,000 to $4,000 to remove the paint, including staff time and the conservationist's $2,500 fee. He said Kaibab got a deal on the fee because the conservator already was in the state for another project.

Andy Laurenzi, Southwest field representative for the Center for Desert Archaeology in Tucson, said removing paint from petroglyphs was especially difficult due to the uneven surface of rock.

He said the main goal of any cleanup is to avoid increasing the damage.

"In general, that sounds like good news," he said of the Keyhole cleanup. "It's always a challenge to be able to do it in a way that won't make the situation worse."

Laurenzi believes that recurring vandalism to petroglyphs is often the work of young people who don't understand the importance of the markings.

Often, he said, it happens at sites with easy access where litter such as empty drink cans indicate the site is a hangout for kids who think of vandalism as merely "something to do."

But he said the Keyhole damage didn't seem to fit that profile. Whoever did it packed in the paint and a brush and hiked about 1.5 miles round trip to make their illegal mark.

"Most of rock-art destruction is not that directed," he said, adding, "They made their point, whatever it is. It's unlikely they will strike again."