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Ten Oregon high school football players remain hospitalized as they’re treated for a rare soft-tissue condition that has school authorities puzzled.

Eighteen McMinnville High School athletes experienced “compartment syndrome,” which caused soreness and swelling in their triceps and high levels of creatine kinase, a protein that can harm the kidneys. Three players had surgery to relieve swelling.

Authorities said the cause was not yet known, but the condition can be the result of exercise or the use of certain medications. All but one of the players who became ill worked out last Sunday at the high school’s wrestling room, where one player says the temperature reached 120 degrees.

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Two players were released by Saturday night from Willamette Valley Medical Center.

Rosemari Davis, the hospital’s chief executive officer, said Sunday that the 10 boys still hospitalized were in good condition and would likely be released Monday.

Superintendent Maryalice Russell told The Oregonian newspaper she doesn’t believe the workout from first-year coach Jeff Kearin was excessive. She said she has no evidence that steroids or other supplements were involved.

“I don’t have any information at this time that would indicate that’s the case,” she said. “I’m continuing to look at additional information as it may come my way.”

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