PORTLAND – The top non-elected official of Maine’s largest city is going on medical leave for about a month as he undergoes surgery Monday for early-stage prostate cancer.

Portland City Manager Joseph Gray Jr. was diagnosed several weeks ago. He said he is feeling well and was on the job through Friday.

Gray, 63, underwent surgery two years ago for colon cancer. He said follow-up tests have not turned up problems, and his current illness is not linked to the previous cancer.

During Gray’s absence, Assistant City Manager Patricia Finnegan will serve as acting city manager.