COLUMBIA, Mo. (AP) — Operations have resumed at a Columbia library after it was evacuated because of a threatening message on social media.

Columbia Police Sgt. Chad Gooch says patrons and employees were asked to leave the library for about an hour Tuesday after staff at Daniel Boone Regional Library noticed a series of “concerning” tweets.

After a bomb-detecting unit cleared the building, Gooch said the tweets were deemed not credible. He says no further investigation is planned.

Library spokeswoman Mitzi St. John says the evacuation was made in order to err on the side of caution.

During the evacuation, no one was allowed in or out of Grant Elementary School, which is across the street from the library.