CHICAGO (CBS) — ComEd crews worked all night, after an equipment malfunction sent repugnant black smoke spewing into the downtown air, and knocked out power to several Loop buildings.

The ComEd trucks and vans were parked along Washington and Clark streets all through the night as the work continued.

Around 8:40 a.m. Tuesday, the smoke began billowing from the manhole on Clark Street, between Daley Plaza and the County Building. A malfunction in the ComEd vault below the manhole was the cause.

The Fire Department called a Level 1 Hazmat response for the eruption.

The malfunction apparently damaged a pair of air conditioning lines, causing the smoke and knocking out power to two buildings. There was no fire reported, despite all the smoke

No evacuations were ordered, but pedestrians were asked to stay away so crews could vent the nasty-smelling electrical smoke in the air.

By late morning, ComEd’s problems were increasing. Hundreds of workers were evacuated as a separate issue in almost the very same spot took out power to a half dozen other buildings.

The problems in the vault also cut power to two of four air conditioning lines for the Daley Center courthouse and county office building, and to the entire building at 25 E. Washington St., which houses doctor’s offices and a Bally Total Fitness athletic club.

Crews resolved that issue by 11:30 a.m. before the second outage struck.

During the second outage, the CBS 2 Broadcast Center, a block away at 22 W. Washington St., was on full back-up power through generators. Upstairs from CBS 2, the Morningstar offices were dark.

Power was also cut to the Randolph-Wells Building, an office building at 205 W. Randolph St.; the Goodman Theatre Building at 180 N. Dearborn St.; and the Mentor Building at 6 E. Monroe St., which houses an American Apparel store and condos, the Sun-Times Media Wire reported.

Power had been restored to all buildings by the 6 a.m. hour Wednesday.

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