CHICAGO (CBS) — A junior high school in south suburban Calumet City will be closed for the fourth day in a row on Friday, after mold was detected in the building.

Mold forces school closures at Calumet City District 155.

Calumet City School District 155 closed all three of its schools as a precaution on what was supposed to be the first day of school Tuesday, after mold was detected at Wentworth Junior High.

Woodrow Wilson School and Wentworth Intermediate School reopened Wednesday, but Wentworth Junior High remained shuttered.

The school district has not said what other steps it is taking at the junior high school, but Superintendent Dr. Troy Paraday said “the health and safety of all our students and staff is our highest priority.”

District 155 issued the following statement Thursday morning regarding remediation of mold in the Wentworth Junior High building.

“The remediation and cleaning phase is ongoing.  While the District anticipates this phase will be completed in the near future, the Wentworth Junior High building will remain closed on Friday, August 24, 2018.  The District’s utmost concern is returning students, staff and visitors to a safe and healthy learning environment.  To that end, the District will work with South Cook ISC 4 in preparation for reopening the building. The District will release further information as it becomes available.”