A U.S. citizen has died in an Egyptian prison after being held for more than six years, Egyptian authorities confirmed Tuesday.

Mustafa Kassem was transferred to hospital on Sunday for treatment, but he died on Monday, Egypt’s attorney-general said in a statement.

The statement said the attorney-general has ordered an autopsy to determine the cause of Kassem’s death.

Earlier, the U.S.-funded Al-Hurra TV said Kassem, who was an Egyptian American, had died after staging a hunger strike.

There was no comment from the U.S. authorities on Kassem’s death.

Kassem was arrested in 2013 following the dispersal of a major

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