The fire, reported at 11:53 a.m., has been contained but not fully extinguished as of shortly after 1 p.m., fire department spokeswoman Mindy Talmadge said.
The blaze caused the roof to collapse at the building, which was still smoldering this afternoon, Talmadge said.
Charles Rathbone, assistant manager with Luxor Cab Co., said the fire destroyed a service garage on Upton Street that the company used for maintenance and repairs.
"It's a total loss," Rathbone said.
He said all employees inside the building escaped without any injuries.
However, he said, "We lost a bunch of cars in there, including a beautiful 1938 Plymouth we had hoped to showcase as part of our history."
Luxor was one of the city's first cab companies, operating since 1928.
"It's nothing that money can't fix," Rathbone said of the fire. "Nobody was hurt so we're fortunate in that event."
Employees at other neighboring businesses were also evacuated because of the fire, which prompted the closure of several nearby streets.
The blaze caused a large plume of smoke that was seen as far away as the East Bay.