A fire on the roof on the Macy's building in Union Square sent plumes of black smoke into the air and alarmed area hotel guests Wednesday morning, but crews were able to swiftly extinguish the blaze once they discovered its source.

According to fire dispatcher, calls to 911 started pouring in at around 12:30 this morning, when guests at hotels near the Macy's at 170 O'Farrell Street noticed a large amount of smoke coming from the building.

By 12:41, San Francisco Fire department units had responded to the the area to fight the one-alarm blaze, SFFD said via Twitter.

According to the Chron, "The store was closed at the time, and finding the fire was challenging for crews who were trying to pinpoint the origin of black smoke that was seen wafting into the night sky."

Eventually, however, they determined that the smoke was "a small equipment fire on the roof of Macy's," SFFD says, and quickly extinguished it before it spread into the structure.

According to the SFFD, no one was injured or displaced as a result of the fire.