Fire broke out Wednesday at a private ground traffic control tower under construction at Miami International Airport.
Hot roofing tar spilled from a pot and ignited, Miami-Dade Fire-Rescue spokeswoman Laverne Guillen said.
The fire appeared to be confined to the domed upper deck of the tower, which is part of a costly construction project at the airport.
Firefighters had to approach the fire cautiously because there were propane tanks on the top of the tower, Miami-Dade Fire-Rescue spokeswoman Cristina Armand said.
The structure is a planned American Airlines ramp control tower that would deal only with aircraft on the ground around the passenger gates, said Jim Marinitti, president of the National Air Traffic Controller's Association in Miami.
It will not deal with landing aircraft, Federal Aviation Administration spokeswoman Kathleen Bergen said.
American Airlines had not yet assessed the damage to the tower, which was set to be occupied by the airline in October, said American spokesman Tim Smith.
"I'm sure it will set back the timing of that," Smith said.
One worker suffered burns and was taken to a hospital, but the injury was minor, Guillen said.