Workers found the carcass last week in an air duct on the seventh floor of the century-old Dayton’s building in Minneapolis.

A spokeswoman for the Dayton’s Project, an office, retail and restaurant complex going into the building, said the developers were at a loss as to where the monkey came from, or how it ended up in the air duct.

But a local historical Facebook page posted a picture of the bizarre find in a bid to get to the bottom of the mystery.

Alan Freed, as co-administrator for the Old Minneapolis page, said one of the more likely answers to come from the appeal came from someone who posted up to say a longtime Dayton’s employee had told him a monkey escaped from an eighth-floor pet store into the air conditioning ductwork in the 1960s.