CHICAGO (CBS) — The buzz of air conditioners is back for nearly 3,000 Lincoln Park neighborhood residents who lost power overnight.

The outage affected customers on some of the city’s most affluent blocks in Lincoln Park and Old Town, from Fullerton Parkway on the north to Eugenie Street on the south, and from Stockton Drive on the east to Larrabee Street on the west.

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ComEd crews worked around the clock to fix the problem. On Wednesday night, crews also brought in five generators.

Fire officials say 20 buildings with a total of about 1,400 units were int eh dark.

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The main concern was high-rise buildings, where elderly residents could have become trapped.

And humans weren’t the only creatures of concern. Two good Samaritans walking their dogs had to carry a disabled dog up 20 floors to his home.

“A woman was out here with a disabled dog, and I just had to carry it up 20 flights of stairs,” good Samaritan Bill Gray told CBS 2’s Marissa Bailey. “I took turns with my brother here, each going up – he’d do five, and I’d do five, and then I’d do five, and he’d do five.”

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ComEd believes a faulty underground cable caused the power outage.