Construction dust filled a tunnel at the Pentagon City Metro station Tuesday morning. The incident comes as riders on the Blue and Yellow lines began their first surge-free commute in almost two weeks.

Arlington County fire crews responded to the station just before 5:45 a.m.

Metro officials say trains passing through the area kicked up construction dust. An exhaust system is working circulate the air.

Metro says the haze was also visible at the Crystal City Metro station.

While train service was not affected, some riders mistook the thick haze for smoke and opted not to ride.

For the past two weeks, the Blue and Yellow lines have had altered service as Metro tackles its aggressive, year-long maintenance and repair plan.

A segment of the Blue and Yellow lines was closed between the National Airport and Pentagon City stations for just under a week during Metro's fourth phase of its nine-month-long maintenance surge. The Crystal City station, which is located between those stations, was also closed.

The fourth surge ended Monday. Before that, a segment from National Airport to Braddock Road was closed from July 5 to July 12.