Officials shut down all security checkpoints at Atlanta's Hartsfield-Jackson International Airport for about two hours after a "suspicious device" was detected in a screening machine.

Amy von Walter, a spokeswoman for the Transportation Security Administration, said a possible homemade bomb had been detected at the airport's main checkpoint. No further details were immediately disclosed.

The airport remained open while an airport explosive detection unit was called in, airport spokeswoman Felicia Browder said, but passengers not yet screened were unable to reach the gates for their flights.

TSA workers detected the suspicious item inside a bag just before 2 p.m., Browder said.

Gates reopened shortly before 4 p.m. By that point, there had been no departures for more than an hour at the nation's busiest airport, and all arrivals were delayed at least 90 minutes.

The shutdown came at peak travel time, and at least 120 flights were affected, said Kathleen Bergen of the Federal Aviation Administration.