PHILADELPHIA >> A stroller carrying a 14-month-old girl rolled off a slanted train station platform and fell onto the tracks Wednesday, but the girl’s mother leaped onto the tracks to rescue her with the help other passengers, transit officials said.

"What it looks like to us is that the mother became distracted by something, didn’t apply the brake on the stroller and the stroller was able to move off the platform and onto the tracks," said Scott Sauer, director of system safety for the Southeastern Pennsylvania Transportation Authority.

The accident happened this afternoon at the 56th Street station of the Market-Frankford Line in west Philadelphia. The platform at the station is slanted slightly for drainage purposes, Sauer said.

Surveillance video shows a woman on the eastbound platform with the girl in a jogging stroller, which slowly rolls forward and topples over onto the tracks about 5 feet below. What initially appears to be the girl flying out of the stroller apparently was just a towel or a bag. The stroller comes to rest on the outer rail, which carries no charge. The woman is seen jumping down and lifting the girl to a man waiting on the platform.

Other passengers ran to help, and one used an emergency call box to alert SEPTA police, who held an incoming train at the preceding stop.

The infant was taken to Children’s Hospital of Philadelphia for treatment of a cut on her forehead.

Sauer said during a news conference that watching the video was "gut-wrenching."

"With the stroller moving at such a slow rate of speed, you know, you want to call out to someone, ‘Hey, the stroller’s moving! Somebody grab the stroller,’" Sauer said.

He said the line is one of SEPTA’s busiest, with trains running every six to 10 minutes.

SEPTA police said no charges will be filed but the accident serves as a reminder for other riders to lock stroller brakes when waiting on platforms.