It happened at the Stingray Auto Spa, in the 4700-block of West Chicago Avenue in Chicago's Austin neighborhood, about 1 a.m.
Flames were shooting through the roof when firefighters got there, and the roof had collapsed.
One bystander said the flames appeared to be at least 20 feet high.
RELATED: Firefighter injured in University Village blaze
Nobody was hurt, and the fire was put out by about 2 a.m., Chicago fire officials said in a tweet early Saturday.
S&B @ 0047, 211 @ 0119 4712 -14 W Chicago 1 story auto body shop 100 X 150 partial Bow truss roof. 211 struck out @ 0158. No injuries no transports at present. Fire is out companies doing salvage and overhaul pic.twitter.com/QzM5x8awM0— Chicago Fire Media (@CFDMedia) September 26, 2020
Investigators are still trying to figure out how the fire started.
A firefighter was injured battling a blaze Friday night in University Village on the Near West Side.