CR Anderson Middle School canceled all classes Tuesday because of smoke and water damage caused by a fire Monday afternoon.
The school has also canceled all after-school activities Tuesday, when the building will be closed to students, staff and the public.
School district Superintendent Jack Copps said the water damage appears to be similar in size to the damage caused by an arson fire at Helena High School in November, but he does not yet have an estimate of how much repairs will cost.
"We're talking about a lot of water damage," he said, adding that much of that was in the cafeteria and gymnasium.
The school will not reopen until it has been cleaned up and the sprinkler system is back online. School officials plan to assess the situation mid-day Tuesday to determine whether to keep the building closed another day.
Officials believe the fire was started by a fluorescent light. All of the lighting in the building will be checked as a result of the fire, Copps said.
No students were in the building when the fire started, as classes had already been dismissed for the day.