Five people died and one person was seriously injured in a house fire in Oklahoma City Wednesday morning.

The fire started before dawn on Dec. 26 and claimed the lives of a mother and her four children living in a two-story wooden home. The other person severely injured in the incident was another resident in the building.

"When we got on scene, we had reports that there were children inside," Fire Department Major Tammy McKinney said, according to The Associated Press. "The fire was so intense that we could not make entry and had to knock the fire down before we could make entry. That's when we found the bodies."

The victims who died in the fire include 3-year-old Kara Leon, 5-year-old Matthew Zackary Leon, 7-year-old Samantha Leon, 8-year-old Natalie Leon and their 28-year-old mother Jeanine Bonnet.

Brian Poletto, the 39-year-old boyfriend of the deceased mother, was taken to Integris Baptist Medical Center where he was listed in critical condition after being treated for second and third degree burns.

A third adult, identified as David Ruppert, was renting a room in the home but was able to escape safely. The AP reported that he was awake in his first floor room when he became aware of the fire.

"All I was saw was smoke," Ruppert said when he first investigated the scene. "My eyes were immediately burning. The kids didn't have a chance. If I hadn't been up (awake) already, I'd have been dead too."

The blaze was reportedly caused by a space heater that was put near flammable material. According to NewsOK , the house had no working smoke detectors and the family used numerous space heaters because there was no gas service in the home.

The fire also claimed the lives of the family's three dogs.