TORONTO, Ont. – The principal of a missing Toronto teen’s school made a public appeal Friday afternoon.

Police and the family are growing concerned about Michelle Yu, 18, who was last seen by friends Tuesday around 2:30 p.m. in the York Mills and Chipstead Road area.

In the televised appeal, Clara Williams, principal of York Mills Collegiate Institute, pleaded with Michelle to at least contact a friend to let them know whether she’s safe.

“If you feel you cannot contact anyone, you cannot come back right now, we want you to call one of your friends, call your family. Let us know that you’re okay,” said Williams.

“There’s nothing that we can’t solve. We will do anything to have you back, to hear from you.”

Michelle’s younger sister Nancy was in attendance and said her sister’s disappearance has been agonizing for the family.

“We haven’t been able to sleep and every thought is always about her,” she said choking back tears.

She then sent a message to her sister.

“We just want her to know that we really care about her and we want her home and we believe in her and we know that she’ll be back soon,” said Nancy.

Security cameras captured images of Michelle outside a TD Bank branch located at 354 Bay Street around 6 p.m. Tuesday. She appeared to be alone at the time.

Family members say it is strange because she is not known to use that TD branch.

Michelle was supposed to attend a meeting Tuesday evening, but did not show up for that or for school on Wednesday. She also has a cellphone which she has not been using.

Friends and family members are so concerned that they are assisting police at 33 Division in North York by posting pictures of the missing teen. Students at York Mills have also started a Twitter and Facebook campaign.

Police Constable Victor Kwong, in charge of the case, told 680News this is unusual because there was no family dispute detectives are aware of, Michelle is not a chronic runaway and this is the first time she’s disappeared in this manner.

Perhaps of more concern is the fact that officials believe the girl has a heart condition and did not have her heart medication when she left.

Despite this, they say there has yet to be any evidence of foul play.

“We’re asking for anyone who might know her or her whereabouts to give us a call. Call us at 416-808-3300 or you can always call us on 222-TIPS,” said Kwong.

Yu is described as Asian, 5’7″, with a slim build, 125 lbs, short black hair with one blonde highlight underneath. She was last seen wearing a grey American Apparel hoodie, black pants and black moccasin shoes, and she occasionally wears glasses.

It is believed she may have been headed downtown by subway when she was last seen.