One person has been pronounced dead after a fire broke out at a residence in the Junction Triangle neighbourhood Thursday morning.

Emergency responders were called to 22 Sarnia Avenue, in the Dupont Street and Symington Avenue area, shortly before 9 a.m.

Firefighters immediately headed for the third floor, which suffered "substantial damage," Toronto Fire Services Deputy Fire Chief Jim Jessop told reporters.

Paramedics confirmed that the victim was pronounced dead at the scene.

Jessop said the fire was quickly put out, and an investigation is underway. He could not provide further details about the incident, including the cause of the fire.

An investigator with the Ontario fire marshal's office was expected at the scene later Thursday.

'Get out, there's a fire'

Neighbour Francisco Vidal, who lives in the apartment that takes up the basement and main floor of the three-storey building, said he heard smoke alarms go off in the apartment above, which takes up the second and third floor.

When he heard a commotion upstairs he assumed the residents of that unit, which he described as a rooming house, had everything under control and carried on with his morning routine with his daughter.

"We were getting ready to go to school and the neighbour upstairs came knocking and said, 'get out of here there's a fire,'" Vidal told reporters. "We just did. We grabbed whatever we had."

According to Vidal, police had been at the upstairs apartment hours before the fire broke out for an unknown issue, but it was quiet in the few hours leading up to the blaze.

Meanwhile, nearby Campbell Avenue was closed northbound at Wallace Avenue while police and firefighters started their investigation.