Flights at two major airports in North Texas were temporarily halted Wednesday after air traffic controllers were forced to evacuate a building because of smoke, and the resulting flight delays were expected to continue for hours.

Lynn Lunsford, a spokesman for the Federal Aviation Administration, said smoke was reported in the Terminal Radar Approach Control Center at Dallas-Fort Worth International Airport. The smoke may have come from a nearby construction project, he said.

"The controllers are back in position and the airspace is back to full capacity," Lunsford said by email. "It will likely take some time to work through the delays."

The control center is separate from the airport tower and directs air traffic across a much broader region. That means flights were also disrupted at Dallas Love Field about 15 miles (24 kilometers) away.

Two American Airlines flights and two Southwest Airlines flights en route to the Texas airports were diverted to Clinton National Airport in Little Rock, Arkansas, Clinton airport spokesman Shane Carter said.

Dallas Love Field was for years the primary airport for the city before D-FW began operations in 1973. Love Field is in the city while D-FW is just northwest of Dallas.

A spokeswoman for D-FW was not able to immediately say just how many flights were delayed Wednesday. A spokeswoman at Dallas Love Field did not return a message seeking the same information.

But the online flight tracker Flight Aware shows more than 300 flight delays at D-FW and 17 cancellations. Love Field had more than 70 cancellations and about 80 flights delayed.