BOSTON (CBS) – Boston mobster Whitey Bulger has been moved from a prison in Florida to one in Oklahoma.

It’s not clear why, but the 89-year-old’s declining health may be a factor.

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The Boston Globe reported that “Bulger’s health has deteriorated and he is expected to be moved to a federal prison medical facility.”

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The U.S. Bureau of Prison’s website says Bulger is at the Federal Transfer Center in Oklahoma City. There are 1,576 total inmates there, both male and female.

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Bulger is serving a life sentence for 11 murders.