One of the players, Josh Nice said, "I was just kind of shocked this was happening to us, like we were dropping like flies from practice."
Three players needed emergency surgery. The diagnosis was "compartment syndrome," which occurs when pressure within a muscle group, called a compartment, increases to an abnormally high level.
The increased pressure within the muscle compresses nerves and blood vessels, cutting off blood and oxygen flow and creating the risk of permanent nerve and muscle damage.
Fullback and linebacker Jacob Montgomery said he first experienced a tightness in his triceps and forearms on Tuesday.
"They swelled to the verge of popping," said the 17-year-old high school senior. "I thought it was just swelling from an intense workout."
All 24 players treated at the hospital had elevated levels of the enzyme creatine kinase. Muscles release CK when they're injured. If not treated, high CK levels can lead to kidney failure.
"The fact that 12 or 13 kids are getting this all at the same time is a little strange," said Dr. Jordan Metzl of Hospital for Special Surgery in New York.
The team was at football training camp where temperatures reached triple digits.
The football players were taking part in an immersion camp organized by new coach Jeff Kearin to get ready for the season. He defends his workout program.
"We believe it was a strenuous work out wasn't excessive," said Kearin.
Officials will look at whether high temperatures played a role, water sources and what the kids had to drink, including power mixes.
Questions are being raised to see if performance enhancing drugs or legal supplements, like creatine are responsible.
"None of the people I was around were taking any kind of supplements or steroids," said Montgomery.
The athletes are not being tested for steroids. But officials are testing for various supplements. Those results are due back as early as Tuesday.