NORMAL - Students were back in class Tuesday at University High School, one day after paintball vandalism prompted administrators to cancel school because the greasy paint made floors slippery. | Video

Hundreds of paintball splotches, mostly in the school colors of Pioneer green and gold, were found on lockers, brick walls, water fountains and doors throughout the school early Monday.

Illinois State University building service workers spent the rest of the day cleaning up the mess at the lab school. They said the greasy paint wiped off fairly easily, but there was a lot of it to clean up.

Classes were canceled because the greasy paint made floors slippery, said Jay Groves, ISU spokesman.

'Our facilities crew took care of it -it took several people the better part of the day-it took some sweat equity." Groves noted the clean-up took away time from other work that need to be done. He said there was no permanent damage to anything.

"The paint itself doesn't adhere," said Jeff Billington, an ISU building service worker cleaning up the mess Monday.

No paint was splattered on photos or unprotected art, Groves said. No words were painted on school property.

"All things considered, it could have been worse," said Assistant Principal Steve Wilder.

ISU police took photographs of the scene Monday.

Illinois State University Police Chief Ronald Swan said some areas of the school may have to be repainted to cover up marks from the paintballs.

"Some people have used the term 'prank,'" Swan said. "And when I look at that - the term 'prank' - I look at criminal damage, the defacement of state property, and I see a crime."

Swan said his department is investigating the damage, though there are no concrete leads at this point. He previously said the vandals entered the school through an unlocked door, and he wanted to know how or why the door was unlocked.

A teacher who routinely arrives at the school at 5 a.m. discovered the damage and notified officials.

Parents, staff and students were alerted through the school's emergency notification system that classes were canceled.

ISU police are asking anyone with information about the vandalism to call (309) 438-8631.

The last day of school and graduation ceremonies will take place on Friday, as planned. A revised exam schedule was set, and details of the schedule change are available on the school's Web site at www.uhigh.ilstu.edu.

Reporters Greg Cima and Sharon K. Wolfe contributed to this article.