A woman was struck and killed Friday night as she ran onto a set of railroad tracks to save her dog from an oncoming commuter train, police said.

The woman, who police described as in her 40s and from out-of-state, was standing on the platform of the Bryn Mawr station about 6 p.m. when her dog got loose and bounded onto the rails, said Lt. Bernard D'Amour of the Lower Merion Township police.

The woman chased her pet onto the tracks as an eastbound SEPTA R5 pulled into the station. She was killed instantly, D'Amour said.

The dog was recovered without injuries and taken to an animal hospital.

Eastbound commuter service on the R5 Paoli-Thorndale line has been suspended as investigators probe the scene. Outbound trains have been delayed 20 minutes. Passengers aboard the train that struck the woman were shuttled to their destinations by bus, Busch said.

Contact staff writer Sam Wood at 215-854-2796 or samwood@phillynews.com.