A man has suffered burns to one-fifth of his body after a propane tank exploded on the roof of a Don Mills office building.

Toronto Fire says the blaze is under control after the fire broke out on the roof of a Royal Bank building near Don Mills Road and Lawrence Avenue just after 10 a.m. Witnesses say there were roofers working at the scene.

Toronto Fire's Mark Fitzsimmons says a worker was on a hoist going from the roof to annother structure when his cabling became entangled with a propane tank.

The worker fell about four to five metres, toppling the propane tank and causing a fire.

Const. Tony Vella says the male victim in his twenties was seriously burned.

The Ministry of Labour and the Fire Marshal have been called to investigate.