HARVARD – Students at Crosby Elementary School in Harvard were kept in their classrooms for more than an hour Monday morning after a shell casing was found in the cafeteria, police said.

Members of the Harvard Police Department were called to the school at around 7:45 a.m. for a report of a .22-caliber shell casing being found by maintenance staff on the cafeteria floor, according to a news release.

The students were kept in their classrooms as police and District 50 staff searched the school for any other suspicious items, activity or people, Harvard police Chief Dan Kazy-Garey said. Nothing was found, and the school day later resumed.