BOSTON (CBS) – The Union Oyster House was evacuated Thursday night after a fire broke out outside the city’s oldest restaurant.

Fire crews responded to the restaurant at about 8:30 p.m.

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The fire was quickly extinguished, but firefighters had a hard time getting the smoke out of the building due to the lack of windows.

Firefighters outside Union Oyster House (WBZ-TV)

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Deputy Fire Chief Robert Calobrisi says firefighters could have broken some windows to let fresh air in, but they “didn’t want to disturb the historical significance” of the building.

“I don’t even know if they can replace these windows,” Colobrisi said. “We tried to weigh on the side of caution.”

No injuries were reported. The cause of the fire is being investigated.

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The Union Oyster House is the oldest restaurant in Boston and the oldest restaurant in continuous service in the U.S.