Charlie Murphy Kept Illness Secret from 'Power' Cast and Crew

Charlie Murphy kept his battle with leukemia so private, most people who worked with him on "Power" had no idea he was sick.

Production sources on the show -- which stars 50 Cent -- tell us they had no idea Charlie was dealing with cancer. We're told he never told anybody on set and put in the work like everybody else.

Charlie played a prison guard named Marshal Williams on the show.

Family sources tell us Charlie only disclosed his cancer battle to very close friends and family members. We're told he said he didn't want his illness to define him.

And, we're told, even the family members who knew he was struggling were shocked when he died ... they didn't know the situation was that desperate.

A rep Starz, where the show airs tells us, "Starz sends our deepest condolences to Charlie's family and friends. He joined 'Power' for our upcoming season, and his talent shines in every scene. We were fortunate to have worked with him."