ST. PAUL (AP) -- Minnesota's governor says he suffered lung damage while recovering from back surgery, keeping him at Mayo Clinic for more than a month.

Gov. Mark Dayton underwent two spinal fusion surgeries last month to improve his leg strength and had been expected to be released within days. He hasn't been seen publicly since his first surgery Oct. 12.

The 71-year-old governor said in an emailed statement Thursday that post-surgical complications damaged his lungs, but he provided no details. He says he is staying at Mayo on his doctor's recommendation to rehabilitate his lungs and that he expects to return to St. Paul in the coming days.

Dayton's office hasn't responded to a request for more detail on the governor's health.

Dayton says he's been in constant contact with commissioners and staff.