Sheshleen Datt, 18, talked to CBC News Friday about being attacked at the Nanaimo SkyTrain Station earlier in the week. (CBC)

A teenaged girl was beaten, threatened with a knife and robbed by six other girls inside a Vancouver SkyTrain station on Tuesday, CBC News has learned.

"I was walking off the SkyTrain. I was on the phone, talking to one of my friends. I completely didn't notice that anyone was following me," Sheshleen Datt told CBC News Friday.

Datt, 18, said a pack of teenaged girls followed her to the bottom of the stairs at Nanaimo Station then attacked her around 9:30 p.m.

"They tugged on the back of my purse and they yelled, 'Hey!'" she said. "I turned around and … I get a punch in my face."

The swarming took place in front of a security camera at the station's front entrance, Datt said. She got away and made it around the corner to her mother's waiting car and phoned 911.

A swarming took place around 9:30 p.m. Tuesday inside this SkyTrain station in Vancouver. (CBC)

Vancouver police arrived at the station and tracked down her missing purse and a knife. Datt said police caught six girls shortly after.

Vancouver Police Department spokesman Const. Tim Fanning told CBC News Friday that charges were considered against two of the girls, but it was decided that there's not enough evidence to proceed.

Fanning said police were unable to identify any of the teen's attackers on the security videotape that was supplied by TransLink.

Drew Snider, a spokesman for TransLink, said the security camera at issue was not working properly because of a technical glitch in the system.

Snider said it's not feasible to have transit police everywhere in a station.

"The people, if they really want to commit the crime, are going to wait until the attendant, the security person or the police officer isn't looking and then do their dirty deed," Snider said.

TransLink said SkyTrain passengers are encouraged to carry pink whistles handed out by the transportation authority so they can alert security if they are concerned for their safety.

The whistles are available at the Collingwood Community Policing Centre on Joyce Street. More than 1,000 whistles have been distributed since the introduction of the safety initiative last May.