It happened at the Momolicious food truck in Union Square around 8:35 p.m.
Crews arrived at the truck near Stockton Street and Geary Boulevard and discovered three employees injured when something on their stove burst, San Francisco Fire said.
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Fire officials say they all had burns and were taken to the hospital.
Streets were briefly closed for the investigation, but have since reopened.
Bay City News contributed to this report
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