Tufts University has begun an inquiry after 12 men's lacrosse players were diagnosed with a rare and potentially fatal muscle ailment after a practice guided by a graduate who had completed Navy SEAL training, Fox News reported.

The institution acknowledged in a statement to The Associated Press that five students were still hospitalized with Rhabdomyolysis, following a 45-minute workout on Monday.

Patrick Collins, director of media relations, expressed words of consolation to families and added that all team practices have been postponed until medical evaluations are made for every team member. 

According to AP, the activity was guided by a university graduate who had previously undergone Navy SEAL training. The graduate was not named.

Collins informed The Boston Globe that seven athletes had been released from the hospital after getting treatment. He said that 50 pupils participated in the practice, and head coach Casey D'Annolfo was not there.

According to the Cleveland Clinic, rhabdomyolysis induces muscular breakdown and can result in muscle death. If this occurs, toxins from muscle fibers can enter the circulatory system and cause kidney injury.

It is developed by 26,000 people in the United States annually.