A missing Michigan 15-year-old was last seen near an Ann Arbor high school on Jan. 27, according to authorities.

Adriana Davidson — who also goes by Addy — did not return home after attending school on Friday, at which point her family began looking for her but was unable to locate the missing teenager, the Washtenaw County Sheriff’s Office (WCSO) reported.

Davidson's friends last saw her around 11 a.m. outside Pioneer High School in Ann Arbor, according to WCSO.

Her brother, Anthony Lopez, said someone found the 15-year-old's phone near the high school's tennis courts on Friday and returned it to Davidson's friend. 

HARMONY MONTGOMERY CASE: MISSING NEW HAMPSHIRE GIRL'S FATHER ADAM INDICTED ON 2ND-DEGREE MURDER CHARGE

Missing Adriana Davidson

Davidson is described as 5 ft., 2 in. tall, weighing 100 lbs. She was last seen wearing black, slip-on Ugg boots. (WCSO)

Lopez is also pushing for authorities to release video footage of his sister on a public Ann Arbor bus called "The Ride" traveling on route 29 on Friday afternoon. 

CASSIE CARLI'S EX-BOYFRIEND INDICTED IN ALABAMA FOR KIDNAPPING RESULTING IN HER DEATH

Davidson's family told 7 Action News that Davidson didn't feel well when she got to school on Friday morning and left school shortly after arriving. Video footage apparently shows her returning to school on "The Ride" bus later that afternoon but does not show her going inside the school building.

Missing Adriana Davidson

Missing Adriana Davidson was last seen at Pioneer High School in Ann Arbor, Michigan, on Jan. 27. (WCSO)

"A student told her best friend that they saw her at the bus stop with a man in a black sweatshirt & black pants & ‘they didn’t seem like they knew each other’ but who knows," Lopez wrote in a Saturday update, along with a flyer showing photos and a description of Davidson.

ACTOR JULIAN SANDS IDENTIFIED AS MISSING HIKER IN CALIFORNIA

WCSO Director of Community Engagement Derrick Jackson told 7 Action News that there are "definitely some suspicious pieces to this" missing persons case.

Davidson was reported missing to the sheriff's office around midnight on Sunday, at which point authorities began an active search for the 15-year-old girl.

Missing Adriana Davidson

Adriana Davidson was reported missing to the sheriff's office around midnight on Sunday, at which point authorities began an active search for the 15-year-old girl. (WCSO)

"Everyone please keep posting these pics of Adriana to keep this viral and flooding the internet to keep this fresh in peoples minds we are making progress, so please keep the posts coming and thank you everyone truly thank you!" the 15-year-old's father, John Davidson, wrote in a Monday morning Facebook post.

CLICK HERE TO GET THE FOX NEWS APP

Davidson is described as 5 ft., 2 in. tall, weighing 100 lbs. She was last seen wearing black, slip-on UGG boots.

Authorities are asking anyone with information about Davidson's whereabouts to contact the Washtenaw Metro Dispatch at 734-994-2911 submit anonymous tips to 734-973-7711.