Multiple Tufts University men’s lacrosse players were hospitalized last week with a life-threatening muscular ailment after participating in a Navy SEAL-style exercise, the school revealed.

According to university spokesperson Patrick Collins, 12 university men’s lacrosse players received a diagnosis of rhabdomyolysis (rhabdo), a potentially fatal muscle condition, following a team practice on Monday, September 16. Five of the players required hospitalization.

Collins reported that a Tufts alum who had completed Navy SEAL training guided the voluntary, supervised 45-minute workout. According to the university, approximately 50 team members participated in the workout, and the number of verified cases and hospitalizations may fluctuate.

Medical personnel are currently treating the hospitalized team members, according to Collins. “Our thoughts are with the players and their families, and we are hoping for their quick return to good health under the care of local medical experts,” he told reporters.

“Meanwhile, we are closely monitoring the condition of the rest of the team and have postponed all team practice activities until each team member has been evaluated and medically cleared to return to participation,” the coach said.

According to Collins, Tufts University intends to investigate the event and will “conduct a thorough review as soon as possible, to take any steps needed to support the safety of our student-athletes.”

According to the Centers for Disease Control and Prevention, rhabdomyolysis is a potentially fatal medical disorder that happens “when damaged muscle tissue releases its proteins and electrolytes into the blood,” most commonly due to heat or abuse. According to the Cleveland Clinic, the muscle tissue breaks down and releases a harmful protein called creatine kinase into the bloodstream, but the illness is curable, usually using IVs to flush the proteins out of a patient’s system.