TORONTO - Police are urging people in a three-kilometre radius of the apartment building where a missing Toronto girl lived to search their properties for signs of her, as they check reported sightings.

Staff Insp. Larry Sinclair told a news conference today police have stepped up the search to a Level 3, which allows them to call in outside units for assistance.

Mariam Makhniashvili, 17, was last seen by her family when she left for school with her brother on Monday morning (near Bathurst Street and Eglinton Avenue West).

She did not arrive home from Forest Hill Collegiate and the school principal said Miriam was not in any classes.

"This to the best of our knowledge is completely out of character for her," he said, as he explained why the search level has been upgraded.

"She's been in Toronto for less than 90 days, to the best of our knowledge she has no friends, and her only relatives in Canada, North America, are her parents and her brother."

He repeated an appeal for the girl to contact police to let them know she is safe.

Her parents have said there was no dispute that would have prompted Miriam to run away, and police say they have no evidence to the contrary.

"There's nothing to lead me to believe that there's anything strained with her relationship with her parents," said Det. Steve McIlwain, the lead investigator in the case.

He added while police say there is no evidence of foul play, police are not ruling anything out.

McIlwain said there were no new leads he could discuss, but confirmed tips received by police "from all over Toronto" include reports of people seeing the girl.

"Those are currently being investigated and will be evaluated once the investigators report back," he said

The parents lived in Los Angeles for five years before moving to Toronto, while the girl and her brother lived with their grandparents in the Republic of Georgia.

The family was reunited when the parents moved to Toronto in June.

Police have contacted relatives of the girl in Georgia to learn more about her, and say they are looking at the possibility she may have encountered problems with students of Russian background because of the Russia-Georgia conflict.

"That's something we're looking at now but right now we're treating it as a missing person and hopefully we'll get some evidence that she's safe and sound," Sinclair said.

The girl is 5-foot-3 with 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.

Anyone with information is asked to call 416-808-5300 or Crime Stoppers anonymously at 416-222-TIPS.