CHICAGO (CBS) — City officials have shut down the northbound lanes of Lake Shore Drive at the bridge over the Chicago River, at least through the evening rush on Monday, due to a “structural emergency.”

City crews fixing a nearby light pole spotted at least two cracked steel beams late Monday morning, and reported the problem. No injuries and no damaged vehicles were reported.

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The city’s Office of Emergency Management and Communications said all northbound lanes on Lake Shore Drive were closed between Monroe to Grand as a result, and advised drivers to use an alternate route.

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The Chicago Department of Transportation said crews were working to install a “shoring tower” under the bridge as soon as possible, but the bridge would remain closed at least through Monday’s evening rush, possibly longer.

The ramp from Randolph to northbound Lake Shore Drive has been closed. Vehicles are being detoured at Monroe, to Columbus Drive, north to Lower Wacker Drive, and back to Lake Shore Drive.

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The southbound lanes of the bridge were not affected.