A Texas high school football coach in the Dallas-Fort Worth metro area was placed on administrative leave this week after several students had to be hospitalized following a workout, school officials said.

In an email to parents Tuesday, Principal Todd Bradford of Rockwall-Heath High School in Heath, Texas, said that head coach John Harrell required the students to “perform multiple push-ups” during an offseason football program on Jan. 6. 

Three days later, on Jan. 9, several players’ parents reported to the school that their children had required “medical attention,” Bradford wrote, “and in some cases, hospitalization.”  

The details of the workout, along with the exact conditions of the players, was not provided. It was unclear how many players required hospitalization. 

Harrell was placed on leave, Bradford said, and the Rockwall Independent School District hired an “independent third-party investigator” to look into the incident. 

The team’s players took park in a “recovery workout” on Jan. 9, that included a “light warm-up and light stretching,” Bradford said.  

The principal also listed several symptoms that the players should look out for, including being unable to bend or extend their arms, nausea, loss of consciousness, vomiting, dark urine and abdominal pain. 

There has been heightened attention to the health of athletes after Buffalo Bills safety Damar Hamlin suffered an on-field cardiac arrest during a Jan. 2 football game against the Cincinnati Bengals. Hamlin was administered CPR on the field by medical personnel before being loaded into an ambulance and rushed to the intensive care unit of a Cincinnati hospital, where he was sedated in critical condition for several days.     

The team has described Hamlin’s recovery as “remarkable.” He was transferred to a New York hospital earlier this week, and was discharged on Wednesday. 

Last weekend, five men’s baskeball players at Concordia University Chicago were hospitalized following a rigorous workout. CBS Chicago reported Thursday that the school initially placed coach Steve Kollar on leave, but he was allowed to return to the team following an investigation.