A Regina firefighter crashed through the floor of a house hit by fire Thursday morning — landing on the floor below — but survived without serious injury.

It happened early in the morning at a house at 1763 Toronto St. The firefighter had been on the second level of the house when the floor collapsed and he fell through to the first floor.

He wasn't seriously injured and remained on the job, fire officials said.

Fire in main floor bedroom

The alarm call to the two-storey home east of the downtown came in at 2:18 a.m. CST.

fire 1763 toronto street regina jan 18 2016

An earlier fire Monday evening was contained to the front porch of the home, but forced the residents out. Thursday morning's fire caused extensive damage to the interior. (Glenn Reid/CBC)

"We were on scene within four minutes and we had a pretty good fire going in the main floor bedroom," deputy chief Layne Jackson told CBC News.

Firefighters were able to bring the fire under control relatively quickly but soon discovered it had spread.

"It got into some concealed spaces in the walls and in the attic and became quite stubborn to completely extinguish, so we were there for some time," Jackson said.

Crews finally finished cleaning up at the scene around 6.

The house is next to St. Basil's Ukrainian Catholic Church on Toronto Street.

2 fire calls to house in three days

It's the second time this week Regina crews have been called to a fire at 1763 Toronto St.

It also happened on Monday afternoon. That time, crews were able to contain the flames to the front porch area.

An investigation of Monday's incident found that fire had been intentionally set.

The damage was much more extensive in the Thursday morning fire, extending through multiple floors and into the attic.

An inspector was on scene in the daylight and Regina City Police were called in as well. A news release from the fire department called it a "highly suspicious" fire.

The house had been vacant since Monday morning's fire.