Mariam Makhniashvili can be seen at the north entrance to Union Station at 11:15 a.m. on Sunday. (Toronto Police Service)

Toronto police have released 15 seconds of security camera video that they hope may help in their search for missing teen Mariam Makhniashvili.

The video was taken as Mariam and her brother arrived at Union Station on Sunday, Sept. 13, at about 11:15 a.m.

The two were on their way to Marilyn Bell Park "to assist as volunteers with a YMCA program associated with dragon boat races," police said in a news release Wednesday.

The video shows Mariam in a blue top and blue jeans and carrying a knapsack as she approached the station from the north entrance on Front Street, then entered the concourse.

The video is the most recent image of the 17-year-old, who disappeared Monday, Sept. 14.

Police have not been able to explain the teen's disappearance. This week one of the investigators said it was "definitely a mystery."

A Grade 11 student, Mariam was in her first year at Forest Hill Collegiate Institute. She left her home to walk to school with her brother on Sept. 14 but never made it to class.

Police said she and her brother separated at the back door of the high school. Mariam walked toward the front entrance but was not seen again.

No friends in the city

According to investigators, there were no surveillance cameras outside the school, the teen did not have a cellphone and she was not carrying her passport when she vanished. All she had with her was her school identification.

Mariam and her younger brother, George, moved from the Republic of Georgia to Toronto in June.

Police said to the best of their knowledge, she had no friends in the city, and her only relatives in Canada are her parents and her brother.

While police believe there is no evidence of foul play, they are not ruling anything out.

Police also said that information made public Tuesday about her father's brush with the law in Los Angeles is not relevant to the case. Vakhtang Makhniashvili was charged with committing a lewd act in front of a daycare in Los Angeles last November and was acquitted in April.

"We were aware of that information at the onset of the investigation," Const. Tony Vella told CBC News. "He is not classified as a suspect or a person of interest."

Mariam is five feet three inches tall and has light-brown, shoulder-length hair and brown eyes. She was last seen wearing black pants, a light blue shirt and a dark blue jean jacket.

She was carrying a large black backpack with a green stripe.