Updated 02/06/13 – 4:41 p.m.

CHICAGO (CBS) — Thirteen minutes. That’s how long a door aboard a moving Metra train stayed open Tuesday evening before a conductor discovered the problem.

The incident was captured on cellphone video by a Chicago Tribune reporter who was aboard the Naperville-bound train.

Tribune reporter and editor Rob Manker said, after he boarded the BNSF Railway line express train to Naperville, one of the two doors in the vestibule closed, but the other stayed open, even after the train began moving.

“As a journalist, you ask, ‘Is this a story?’ and it appeared to be an issue of public safety, so I rolled camera,” Manker said. “It was kind of harrowing. As you look down at those tracks, estimated to be going about 60 miles an hour on the train, it definitely seemed to be a question of safety.”

Manker said any number of things could have gone wrong if the door stayed open, such as an unattended child entering the open train vestibule while the train was still moving.

“The one thought I had was, one passenger who came along and tried to close the door themselves, which I cautioned them against,” Manker said.

Manker said, more than ten minutes into the ride, a conductor taking tickets, closed the door.

“I saw that he was startled to see that the door was open. He went over to it, to the opening, and gave it a good tug or two himself, until he was able to get it closed,” Manker said.

He said he kept a safe distance from the open door at all times while recording video of the incident.

Metra said an inspection found the door was blocked by ice, and a heater in the door was not operating properly. The problem was fixed, and the train car was back in service.

BNSF was investigating the actions of the train crew.

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