Toronto police have executed a search warrant at two public libraries as part of their search for missing teenager Mariam Makhniashvili.

Police went to the Forest Hill branch Tuesday morning and seized six computers. They also seized 21 computers from the Barbara Frum branch.

Sources have told CTV Toronto that investigators believe the teen, who turns 18 today, may have used the computers to communicate with people.

They want to try and determine who Mariam might have been communicating with and what her mood was at the time.

The library is located at 700 Eglinton Ave. W., very near Mariam's high school and an easy walk from the family home at 20 Shallmar Blvd. The Barbara Frum branch is to the north at Bathurst and Lawrence Ave.

This is the first major development since someone found the girl's backpack earlier this month still loaded with school books at 130 Eglinton Ave. E, just over two kilometres east of Mariam's school.

She had last been seen at the school on Sept. 14. She walked there with her brother George. As they approached the school, Mariam told him she would be going in the front door as it was closer to her first-period class. They parted company -- and then she seemingly vanished.

One witness in the Yonge/Eglinton area said she's convinced she saw Mariam with a male in his 20s more than a month ago, but other than the backpack's discovery, police have found no concrete evidence of her whereabouts.

Police say they have no evidence pointing to an abduction or to suggest she ran away -- something her family has said would be out of character for the girl.

Her father, Vakhtang Makhniashvili, told Canada AM on Tuesday that it is "impossible to imagine that she could run away or walk away for five minutes even, or miss school."

Mariam and George came here from the Republic of Georgia in June to reunite with their parents, who had been working in the United States for the previous five years.

The family has no relatives in Toronto. They say Mariam has not been in contact with her friends and family back in Georgia. Her passport is still at home.

Vakhtang said his family will be praying that her birthday is the day Mariam returns home.

Anyone with information is asked to call Toronto police at 416-808-5300, or to call Crime Stoppers at 416-222-8477. Members of the public can also send in tips online at www.222tips.com, or they can text TOR and a message to CRIMES (274637).

With files from CTV Toronto's Jim Junkin