The family and friends of Toronto teen Michelle Yu held a press conference Friday pleading for her safe return.

The 18-year-old York Mills Collegiate Institute student was last seen on Tuesday at about 2:30 p.m. in North York near York Mills and Chipstead Roads.

Her cell phone has been turned off since Tuesday, according to the Find Michelle Yu website.

Police released a photo of Yu taken from a TD Bank camera on Bay Street at 6 p.m. on Tuesday.

They say it's possible Yu took a bus out of town, since there are no signs of foul play.

Family and friends have described the disappearance as out of character for Yu. She is a good student with lots of friends who is involved with Girl Guides and her student council

However, Yu's mother, Sharon, said she doesn't think her daughter ran away from home.

"I think she loves us," she said.

Adding to the urgency is the fact that Yu has a heart condition and requires medication, which she does not have with her.

York Mills Collegiate Institute principal Clara Williams spoke at the press conference Friday, saying fellow students held a school assembly Thursday and they were very upset about Yu's disappearance.

"The mood in the school has been one of sadness," Williams said.

Yu's sister, Nancy, said she just wants her sister to know that her family wants her home.

"We believe in her and we know that she'll be back soon," she said.

She said family and friends stayed awake Tuesday night, putting up missing posters at transit stations.

"It feels like it's just been one long day, and we haven't been able to sleep. Every thought is about her," she said.

Yu is described as Asian, 5'7" tall, and about 125 lbs. She was last seen wearing a grey American Apparel hoodie, brown moccasins, and may be wearing glasses.

Toronto police are asking anyone with information to call police or Yu's friends or family.