The Walker Art Center was forced to shut down Wednesday after a main-line sewer backed up and flooded its lower level.

The museum is expected to reopen Saturday. A screening of “Pariah” was rescheduled to 2 p.m. Saturday and “Butch Cassidy and the Sundance Kid” will be shown at 7:30 p.m. on Oct. 13.

Stormwater and sewage began backing up in the lower level bathrooms of the Barnes building during the “wee hours” of the morning on Wednesday, said Annie Gillette Cleveland, museum spokeswoman. Gravity then moved the water into the lower-level offices, she said.

Damage was confined to lower-level bathrooms and offices, but the entire museum was closed.

The cause is being investigated, but it may be related to construction on nearby Hennepin Avenue, Gillette Cleveland said.