As firefighters battled the blaze in the 200 block of Front Street, much of that section of downtown was left in the dark.
Street lights, traffic lights and the kitchens of downtown restaurants were shut down for hours at the height of Friday night business as electricity was turned off for the safety of the firefighters.
The cooking of a Valentine's dinner at The Galley, 203 Second St., came to an abrupt halt, said assistant general manager Joe Rovinsky.
"We were right in the middle of it when we lost power," he said. "Now we're actually cooking on a grill outside because when the electricity goes out it shuts down the gas in the kitchen. You do whatever you have to. You scramble."
Many of the diners and those listening to the Bob Thompson Unit band at the adjoining Adelphia music hall remained after the power was cut, with only candles lighting the businesses.
"I live right around the corner, so I figured my power would be out, too," said James Wright, 28. "Here I can have a drink. ... It's an interesting Friday night."
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Smoke pours from the roof of 284 Putnam St.
Carol Orr, of Marietta, was enjoying her birthday dinner at The Townhouse, 230 Front St., when she heard about the fire.
"Somebody came in and said something was on fire here," she said, noting the power went out later.
"It's sad. There are too many fires on Front Street, and that was somebody's home. That's the worst part," Orr said.
At the Galley and Adelphia, customers and staff anxiously awaited news about the fire but said they were actually enjoying the atmosphere in the dim businesses, where the music still played.
"Folks are making a party out of it," said John Lehman, whose company, Promanco, owns the complex.
In front of the burning building, dozens of people gathered, snapping photos, taking video and huddling together to stay warm.
"I could smell it from pretty far away," said John Richland, of Marietta, who was walking his dogs on the River Trail when he changed course and stopped to see what was happening. "I hope everyone is here out of concern and not for entertainment."
Evan Bevins contributed.