CEDAR RAPIDS, Iowa (AP) _ Shock rocker Marilyn Manson cut short his concert and abruptly walked off the stage when he realized someone had stuck a large yellow smiley face on a stage prop. The resulting rowdiness ended in 23 arrests.

The crowd of 4,765 appeared stunned when Manson _ already the target of criticism this week alleging that his wild, ``gothic″ style influenced the Littleton, Colo., school shooting _ became angry Wednesday and stormed off the stage early.

Some in the crowd became rowdy and swarmed Manson’s tour bus. Police arrested 23 people on charges of assault on an officer, interfering with police, disorderly conduct, trespassing and failure to disperse, police Lt. Jerry Potter said.

Police and security officers at the scene said there were several scuffles between officers and the crowd. There were no reports of injuries. It was not known if Manson was in the bus at the time of the incident.

Inside the Five Seasons Center, 10 people were arrested on charges of public intoxication or possession of a controlled substance. Organizers had beefed up security at the center because of the controversy surrounding Manson.

Jennie Boddy, publicist for the band’s record label, Nothing/Interscope Records, said today she would try to learn why Manson cut short his show.

Potter said Five Seasons Center personnel told him that Manson ``somehow saw (the smiley face) at midpoint of the song and he became very upset.″

He said it was the face, 2 to 2 1/2 feet across, ``large enough to make a presence,″ was stuck on the front of a prop that looked like a pulpit. It was visible to the audience but not, at first, to Manson.

``It struck me as very odd that it would be part of his stage presence when it was so uncharacteristic of everything else he was doing,″ Potter said.

Tammy Koolbeck, marketing director at the Five Seasons Center, said no one in the crowd or the center’s staff could have gotten to the prop to attach the smiley face.

``It was probably put on by one of his people,″ she said.

On Tuesday, hundreds of demonstrators rallied outside a Manson concert in Minneapolis, protesting possible links between his dark music and the Colorado school killings.

At the same time, Manson announced the cancellation of next week’s last five dates of his U.S. tour, saying it was out of respect for the victims of the shootings. Manson, who took his stage name from Marilyn Monroe and mass killer Charles Manson, said he blames the tragedy on ignorance, hatred and access to guns.