The death of a young Muslim-American recruit at boot camp is at the heart of an investigation gripping the U.S. Marine Corps, and raising serious questions about practices at its vaunted, 101-year-old training facility at Parris Island, S.C.

A Marine Corps investigation into the death of 20-year-old Raheel Siddiqui has sparked a broader probe into possible wrongdoing in the same training battalion, extending to allegations beyond his case, Marine Corps officials said.

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