GRAPEVINE, Texas (CBSDFW.COM/AP) – At least 100 flights at Dallas-Fort Worth International Airport have been delayed after some employees were evacuated from a government air traffic control facility because of an undetermined odor.

“It appears that nearby construction work unearthed some sort of backup in a line,” according to Federal Aviation Administration spokesman Lynn Lunsford.

They’re continuing to provide air traffic services at a slightly reduced rate as they rotate personnel in and out of the building.

Air purifiers and fans are in use to circulate fresh air throughout the building, which is just south of the airport.

The FAA website says flights arriving at DFW were being delayed an average of about an hour. FlightStats.com reports at least 100 flights were affected.

The FAA isn’t saying when it expects staffing at the control center to return to normal at DFW, a major hub for American Airlines and its American Eagle regional affiliate

Nobody was hurt.