A dozen men's lacrosse players at Tufts University in Boston have been diagnosed with a rare muscle injury following a voluntary workout conducted by an alum with Navy SEAL training, according to a school spokesperson.

Five players remain hospitalized after being diagnosed with rhabdomyolysis – a condition that results in the disintegration of muscles into the bloodstream. The problem can be life threatening.

'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,' school spokesman Patrick Collins wrote in a statement.

'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,' he added.

Both the number of confirmed cases and the number of those hospitalized could change, Collins said.

Rhabdomyolysis is an injury where a person's muscles break down, according to the Cleveland Clinic. The life-threatening condition can occur after another injury or excessive exercise without rest.

Given the seriousness of the injuries, Tufts is appointing an external, independent investigator to conduct a thorough review as quickly as possible, with a goal of taking any steps needed to support the safety of the school's student-athletes, he said.

The university is still learning about the circumstances that led to the injuries, he said, and cannot provide additional details until the investigation is complete.

The Tufts Jumbos are coming off a Division III NCAA title after beating RIT at Lincoln Financial Field in Philadelphia last spring.