ST. HELENA (CBS SF) — A Saturday night fire raced through the second story of a downtown St. Helena building housing a Bank Of America branch, heavily damaging the structure, authorities said.

A passerby called 911 to report the blaze at about 6 p.m. The caller reported seeing smoke coming from the roof of the building on Adams Street near Library Lane.

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St. Helena Fire Chief John Sorensen told the Napa Register that the fire started on a parapet wall on the building’s second-story roof.

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There was a worker in the building at the time of the fire who was able to escape uninjured.

While firefighters were able to limit the blaze to the second floor, the first floor did sustain major water damage. Firefighters from the St. Helena, Calistoga and Napa County fire departments all helped fight the blaze.

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There were no reports of injuries and the cause of the fire remained under investigation. The fire caused nearly $1 million in damage to the building.