The Ontario Fire Marshal is investigating a suspected case of arson after two fires broke out in the same apartment early Thursday morning.

Firefighters were called to an apartment building at 1011 Lansdowne Ave., near Dupont Street, at around 2 a.m.

A resident of the apartment told firefighters he'd been smoking in bed when the fire started. It was quickly extinguished.

Less than an hour later, firefighters were called back to the same apartment for a separate fire. The same resident told them he'd stepped outside and left the door open when the fire started. He said he didn't know what caused the second blaze, which started near the area where the first fire sparked, Toronto Fire officials said.

The man was transported to hospital, where he is being treated for smoke inhalation.

The Office of the Fire Marshal is investigating the case.