DENVER (KDVR) — A person was able to get past security at Denver International Airport and board a passenger terminal train before being apprehended Monday, the airport said. The trains were shut down during the incident.

“On Monday around 12:40 p.m., an individual entered the sterile area of the airport via the exit lane at Denver International Airport. Airport operations stopped the trains, TSA immediately suspended screening operations in the checkpoint and flight departures were temporarily halted,” a TSA spokesperson said.

“Airport law enforcement apprehended the individual who was on the train on the A concourse platform. The passengers and train were screened with negative results.”

The sterile area is where everyone has been screened, the spokesperson explained.

The individual was able to get down the escalators in the arrivals area, according to the airport. The escalators lead to the underground airport trains.

One passenger who talked with FOX31 said plane boarding was also stopped. The airport says the security incident is being investigated.

The trains were back up and running at 1 p.m. The airport says all passengers and employees are safe.

No further information has been released. FOX31 has a crew at the airport and is working to get additional details.