Toronto fire crews are investigating after a large fire broke out at a building under construction downtown Thursday afternoon.

Fire crews responded to reports of a fire at 384 Richmond St. E, near Queen and Sherbourne streets, shortly after 2 p.m.

Toronto Fire Service said there was a large pile of construction debris on fire on the third floor and another fire on the fourth floor.

There was also smoke billowing from other floors and crews are checking to see if the blaze spread to other areas.

Toronto fire said it is unclear if the building is occupied.

The fire was upgraded to a third alarm at its peak.

Crews have since extinguished the fire on the fourth floor but are still working to extinguish the fire on the third floor at this point in time.

No injuries have been reported.

The cause of the fire is unknown.