No one was hurt Saturday when hot tar spilled over and ignited the exterior roof of the University of Kentucky's central heating plant on South Upper Street.
Lexington Batallion Chief Jeff Nantz said there was "heavy black smoke" at the scene when firefighters arrived at about 9:20 a.m.
"It was a lot more smoke than there was fire," Nantz said. "It looked a lot worse than it was."
Damage was confined to the pot in which the tar was heated, he said. The two roofers were evacuated and were not injured.
The boiler plant provides heat to the campus, but Nantz said there was no interruption of service.
Southbound traffic on South Upper Street was diverted onto Bolivar Street.
Two ladder trucks responded to the scene, as well as multiple other emergency response vehicles. Firefighters began leaving the scene at 10 a.m. Saturday.