Rare bronze casts of Abraham Lincoln's head and hands by Augustus Saint-Gaudens were stolen, and police and museum officials said Saturday they think the theft was an inside job.

"In theory, we just don't know how anyone could have gotten in and done this since the house was closed to the public at the time" and security alarms weren't tripped, said Carol Callahan, curator of the Glessner House Museum on the city's South Side.Callahan on Saturday wouldn't give the value of the set, though she previously estimated it in the tens of thousands of dollars. The set was insured, she said.

Police questioned everyone who was in the museum Thursday but no charges have been filed, police Sgt. Kenneth Januszyk said.

The sculpture, made from a plaster cast taken of Lincoln shortly after he became president, was last seen an hour before the museum closed Thursday. It was discovered missing early Friday by a guide making rounds before the museum opened, Callahan said.

"She actually encountered me in the hall and asked me if I had moved the sculpture," Callahan said. "At that point, I had the horrible feeling that something was wrong."

The tightly guarded museum has an electronic security system, and visitors must phone from the front door to be escorted in. They are also escorted out when they leave. The sculpture was displayed on a desk behind ropes.

Callahan said no tours were conducted Thursday; the only people at the museum that day were officials of the Chicago Architecture Foundation, which owns and administers Glessner House, and office delivery workers, she said.