(AP) -- DETROIT - Parts of central Detroit are blacked out for a second day because of a breakdown in the municipal power system.

Traffic signals were out in downtown Detroit on Sunday, and the Detroit Institute of Arts was closed. WWJ-AM says Cobo Center has partial service Sunday.

The Detroit News says outage has hit public buildings, street lights, traffic signals and the Detroit Medical Center, which get power from the Detroit Public Lighting Department.

The medical center says it's using backup generators.

A spokeswoman for Mayor Dave Bing says DTE Energy Co. is helping Detroit work to restore service.

Karen Dumas blames the blackout on a combination of last week's high heat and humidity and the outdated municipal electrical system.

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