A 71-year-old man imprisoned for more than 40 years after a conviction for kidnapping and sexual assault has died.

The Alaska Department of Corrections says Clayton Morrell died Thursday afternoon at Alaska Regional Hospital.

The department says Morrell had been in custody since 1975. He was imprisoned at Anchorage Correctional Complex since 2014.

Corrections officials say he had been ill for some time and on Saturday was transported to the hospital.

Alaska State Troopers and the state medical examiner's office are reviewing the death.