Police are investigating whether two teens struck by a light-rail train in Edmonton on Tuesday were killed accidentally or whether the incident may have been a homicide.

The fatal collision occurred at about 8:15 p.m. local time, Edmonton police said, between the Stadium and Coliseum LRT stations.

The pair was spotted walking near the tracks with a group of youths moments before the train struck them. The male victim died at the scene, while the female victim died in hospital.

Distraught family members have identified the two victims as Jamie Kootenay and Delia Papastesis. Friends said the couple had been dating for four years.

"I saw both of them yesterday," said Papastesis' sister Janice Randhile.

"All I know is she got hit by a train, and I don't know why," she said, in tears. "It's really hard because she was my baby sister and she's gone."

Homicide investigators have been called in and are trying to determine whether the deaths were accidental or criminal.

"There are some different witness accounts of what actually happened. What they have to do is corroborate that evidence," said Chad Orydzuk, a spokesperson for the Edmonton Police Service.

One witness who did not want to appear on camera said the couple may have been fighting on the night of their deaths.

The witness also said she saw a woman being held down on the tracks by a man who had lain on top of her, and that nearby warning bells were ringing as the train neared.

Randhile said the couple "had their problems," but she didn't know if they were "the cause of what happened."

One of Kootenay friends, Nolan Shone, said he was with the couple Tuesday night and disputed that anyone was held down on the tracks.

Kootenay's grandfather told CTV News that his grandson was a good boy who was very respectful.

Autopsies on the two victims were scheduled for Wednesday afternoon.

Orydzuk said a number of witnesses who left the scene are being asked to contact police at 780-423-4567.

With a report from CTV Edmonton's Sonia Sunger