(Reuters) - Graffiti etched into one of the popular red rock arches in Utah's Arches National Park may be too deep to be repaired, the park's superintendent said on Thursday.

The vandalism, which was discovered by park staff last Saturday and includes names and numbers, spans about six feet on the so-called Frame Arch, park superintendent Kate Cannon said.

The site of the graffiti is near a hiking trail to one of the park's main attractions, Delicate Arch, a 64-feet high sandstone structure that has been known to draw hundreds of visitors at a time.

Authorities have not yet identified any suspects, Cannon said. In a post on their Facebook page, park officials appealed to the public for information that would lead them to the culprits.

Defacing a national park can lead to a sentence of six months in prison and a $500 fine, according to the website for the U.S. Department of Justice.

Cannon said lighter graffiti can be effectively erased by rubbing it down with sand, but this etching was too deep for that process to work.

"In this case, we are going to try filing them but that may still be quite visible if we can't get the color exactly right, and it may not be sustainable," Cannon said. "There's really no way to fix graffiti of this sort."

People vandalizing national parks is nothing new, but she said it seems to have accelerated in recent years. Park rangers and volunteers spend hundreds of hours removing graffiti from the park every year.

Cannon said increasing public awareness about how damaging graffiti is and emphasizing that it is illegal is the only way to stop it.

"It is utterly inappropriate in this place," Cannon said.

(Reporting by Curtis Skinner in San Francisco; Editing by Alan Crosby)