CHANTILLY, Virginia_Fumes from a work site forced air traffic controllers to evacuate their tower at Dulles International Airport near Washington, D.C., and shift to a backup facility for about two hours Wednesday.
The fumes were reported about 10 a.m., and firefighters ordered the tower cleared, airport spokesman Robert Yingling said. The tower was ventilated and the controllers were allowed to return about two hours later, he said.
The U.S. Federal Aviation Administration said a contractor welding in a terminal area next to the tower.
There's a "possibility that fumes from nearby welding went up an elevator shaft into the tower," FAA spokesman Les Dorr said. Four people in the tower were taken to a hospital for treatment.
The incident had a minimal impact on flights, authorities said.
FAA spokeswoman Laura Brown said air traffic controllers were moved to another tower that is normally used to coordinate planes at airport gates. Both towers have the same capabilities, though the backup tower has fewer work positions, she said.