HATTIESBURG, Miss. — An Illinois National Guard member died after suffering heat injuries during outdoor fitness activities at a military base in Mississippi, authorities say.

The 38-year-old man was treated by a medic at Camp Shelby when he showed signs of injuries Friday and was taken to nearby Forrest General Hospital, where he was pronounced dead, said Lt. Col Diedre D. Smith, a spokesperson for the Mississippi National Guard.

The Illinois soldier was at Camp Shelby for a leadership school, Smith said. The Mississippi National Guard is not releasing his name out of respect for his family, she said.

Camp Shelby is just outside Hattiesburg, where high temperatures topped 100 degrees from Friday to Monday, according to the National Weather Service. Humidity increased the heat index by a few degrees.

An 18-year-old Mississippi guard member was also hospitalized for heat injuries after exercising outdoors Saturday at Camp Shelby, Smith said.

The Mississippi guard issued an order Saturday banning all outdoor fitness activities between 7 a.m. and 8 p.m. during the heat.