WATERVILLE — The George J. Mitchell School  was evacuated early Monday because an odor believed to be propane was detected, but later was determined to have been caused by a furnace malfunction.

Crews from the Waterville Fire Department responded just after 8 a.m. to the elementary school on Drummond Avenue to search for the cause of the odor, fire Chief Jason Frost said. He said later that they determined the odor was from the furnace.

Staff, as well as children who were being cared for before school started, were told to leave the building with their belongings. They were taken by bus to Waterville Senior High School. Most children who attend the Mitchell School were just getting off buses when the evacuation was called, so they did not enter the school before going to the high school.

They were returned to the Mitchell School by bus later in the morning.

Waterville Public Schools Superintendent Peter Hallen sent a message Monday to Mitchell School staff and families that said a “strong, fuel-like odor was reported in and around the D-Wing of the school.”

“Out of an abundance of caution we closed the building and relocated students and staff to Waterville Senior High School, where students were able to have breakfast. Our maintenance team, along with the Waterville Fire Department, responded immediately to investigate. It was determined that a boiler misfire in that section of the building caused some fumes to draft back into the boiler room. Comprehensive air testing confirmed that the building was safe, with no detectable levels of carbon monoxide or other harmful fumes. At no point were any smoke, carbon monoxide or natural gas alarms triggered.”

The Mitchell School serves children in grades kindergarten through grade three. The building is connected to a building that houses Educare Central Maine, an early childhood education program that serves children from birth to when they transition into kindergarten.