Mound Westonka High School remains closed through Tuesday as crews try to repair equipment that provides power to the facility's heating, ventilation and air conditioning system.
The mechanical failure affected air handling units that provide ventilation to the school's main academic wings, the gym, and the theater.
Consequently, the high school could not meet indoor air quality requirements, prompting administrators to close the school Monday. Classes are expected to resume Wednesday.
"The district is taking the necessary steps to determine the cause of the failure, and our insurance company has been notified," Superintendent Kevin Borg wrote in a letter sent to families Monday. "We are thankful that the issue was quickly identified and that our students and staff were not put at risk."