Liberty Memorial Central Middle School evacuated a crowd attending a choir concert Tuesday evening and alerted firefighters after a burning smell was detected.

Firefighters at the scene, 1400 Massachusetts St., determined that the cause of the odor was not a fire but a laminating machine in the library media center, according to a news release from the Lawrence school district.

Everyone was then allowed to return to the building.

The district did not have an estimate of how many people were in attendance.