A robber who held up the Sick Kids Hospital Shopper's Drug Mart on Saturday made off with an unknown quantity of money and regular Tylenol, police said.

Police sealed off the exits to the hospital for about 20 minutes on Saturday as they combed the building for the perpetrator.

According to Toronto police Staff Sgt. Jay Frosch, an unmasked man went into the Shopper's Drug Mart on the hospital's main floor at about 11:30 a.m. and pulled out a "fairly large knife."

"He... demanded some cash and things went from there," Frosch told ctvtoronto.ca on Saturday.

Alerted to the incident by security, police quickly put the hospital on lockdown as they searched for the suspect on the premises. They didn't find him and proceeded to move the investigation to the surrounding neighbourhood.

Frosch said there is a good chance the suspect was caught on hospital security footage.

The suspect is described as a white male in his 40s, with brown hair and a goatee. He was wearing a blue and white Toronto Blue Jays cap, a two-tone beige jacket, grey or tan pants and white shoes. Anyone with information is asked to call Toronto police.

The Sick Kids Shopper's Drug Mart location is owned and operated by the hospital.