LAS VEGAS -- The famous “Welcome to Las Vegas” sign was vandalized, and public works officials believe it happened at some point over the weekend.

Residents, tourists and Mayor Oscar Goodman were infuriated when the graffiti was discovered Monday morning.

In spite of the man-made blemish, tourists were still posing for pictures in front of the sign Monday night. Some said they had come a long way to snap their photos at the sign, and they’re not happy.

Initials, scribbled in red marker, showed up in the middle of a Las Vegas landmark.

“It just makes me sick, why somebody would do that,” said tourist Marla Seip.

Tourists were grinning and bearing it, knowing the graffiti was marring their perfect shot.

“It is ruining the picture that I want to take,” said Kelsey Powers, who was visiting from Texas.

Discovered by maintenance workers, the meaning of the graffiti, and who put it there, is unknown.

While the site has been the target of vandals in the past, the Clark County Department of Public Works said this was the first time the sign itself has fallen victim to taggers.

Tourists said they think it's a slap in the face.

“Would they like somebody coming into their house and doing it? Or their cars? Or whatever? No,” said Gayle Nungesser.

Goodman said he was furious over the vandalism, saying, “When they graffiti'd my tortoise, I said, 'Off with their thumb!' This deserves 'Off with their head!’"

“A lot of tourists come here and want their picture taken by a famous sign, and it kind of ruins it a little bit,” said Spencer Johnston, of Utah.

“We want to show our family at home with us standing in front of the sign, and they're going to see that as well in the picture,” said Kelly Gainty, visiting from Scotland.

“Hopefully, there's something that can be done to catch the people,” Nungesser said.

There were no surveillance cameras at the Las Vegas sign.

Maintenance workers will be cleaning up the graffiti Tuesday morning.

Anyone with information on the vandalism is asked to call the Clark County Graffiti Hotline at 702-455-4509.