Austin Powers Villain Murder Investigation

Prison officials tell us ... Joe Son has been placed in solitary confinement for the time being, citing "safety reasons."

We're told Son was originally housed in an area reserved for new prisoners -- but after he was named a suspect in the death of his cellmate, Son will be on his own while prison officials investigate.

During his solitary confinement, Son will be allowed to enjoy 10 hours of yard time a week -- and he'll also have regular shower privileges.