CEDAR RAPIDS, Iowa (AP) — Officials with an eastern Iowa school district say students and staff at an elementary school may have been unwittingly exposed to asbestos for several months.

KCRG-TV reports that College Community School District sent a letter to parents Wednesday about the asbestos concern at Prairie Crest Elementary School.

Winter break will be extended for clean-up measures.

The letter states that a contractor replacing carpet failed to properly abate asbestos within the carpet glue before removing it during construction work in June.

The asbestos wasn’t detected until this month. Subsequent testing on Monday was clear of asbestos, but the district says it will continue to move ahead with clean-up efforts.