Air travel was disrupted to and from Chicago’s Midway Airport Tuesday after several air traffic control tower technicians there tested positive for the coronavirus, the FAA said.

The diagnoses led the federal agency to temporarily close the tower, but it was later opened with limited access, according to the Chicago Department of Aviation.

“Midway remains open, but operations will be limited until further notice,” the Chicago Department of Aviation said in a statement.

The tower had been cleaned according to standards set by the Centers for Disease Control and Prevention before reopening, the FAA said.

All workers at Midway’s air traffic control tower are expected to be tested for the virus, according to the National Air Traffic Controllers Association.

“NATCA is adamant that the testing must occur immediately and is hopeful there will be no additional COVID-19 infections,” the labor union said in a statement.