University spokesman Larry Hincker said police interviewed witnesses who saw and heard people setting off firecrackers or some other explosive material in or near a trash bin near the dormitory, which is home to about 1,000 students.
The university has revised emergency reponse procedures after a gunman killed 32 people and himself in a 2007 rampage. After criticism over its response to those shootings, the university instituted an e-mail alert system and other safety procedures to notify students immediately of danger.
Mina Sharobim, a sophomore resident adviser at Pritchard Hall, said he didn't hear any loud noises, but spoke with police officers who were conducting the building search and was tasked with checking student IDs.
"Especially with the things that have happened here, you never can be too careful," he said.