Five Tufts University lacrosse players remain hospitalized after recently training under the direction of a graduate of a Navy SEAL training program, according to a university spokesman.

According to Patrick Collins, Tufts media director, about 50 team members participated in the voluntary, 45-minute training session on campus on Monday. The session was led by a Tufts alumnus and graduate of the BUD/S Navy SEAL training program.

Collins said 12 members of the lacrosse team have been diagnosed with rhabdomyolysis, or rhabdo, which is “a serious condition that can lead to permanent disability or death,” according to the Centers for Disease Control and Prevention. It occurs when muscles break down, often due to overexertion, and release their contents into the bloodstream. Symptoms can be similar to those of heat-related illness and dehydration. The only way to know if you have it is through testing.

Five of the student-athletes are still hospitalized, Collins said, adding that both the number of confirmed cases and the number of hospitalizations could change.

“Our thoughts are with the players and their families and we hope they make a speedy recovery under the care of local medical experts,” Collins said. “In the meantime, we are closely monitoring the condition of the rest of the team and have postponed all training activities until each team member has been evaluated and medically cleared to return.”

Due to the seriousness of the situation, the university said it was engaging an outside, independent investigator to conduct a thorough review “with the goal of taking all necessary steps to ensure the safety of our student-athletes.”

The school said it could not release further details until its investigation was complete.

Tufts University in Medford and Somerville has about 6,700 students. The men’s lacrosse team won its fourth NCAA title in May, defeating RIT.