Shippensburg University announced the cancellation in e-mails to its 7,500 students and 800 employees Thursday after campus police were notified about the box around 3:45 p.m., school spokesman Peter Gigliotti said.
Police later determined the box contained used paper and had been placed next to a trash can outside the building by a university employee, Gigliotti said. Classes resumed today.
"It was an honest mistake," Gigliotti said.
The school's policy requires authorities to investigate any suspicious packages found on campus. Everyone's vigilance has been heightened following a shooting attack earlier this week at Virginia Tech, where a gunman killed 32 people and himself, Gigliotti said.
"We told (students and employees) that if something doesn't feel right, call university police," he said.