Investigators say it appears an old electrical cord caused a house fire that killed three children and an adult in western Iowa. The fire was spotted by a police officer on patrol in Lake City at 1:45 a.m. Tuesday.

Lake City Fire Chief Mel Alcox says the cord was attached to a hanging lamp located over a hide-a-bed couch. The cord apparently got caught in the couch and shorted out, sparking the fire. Twenty-two-year-old Tyra Pierson and her 11-month old son, Xavier, died in the fire, along with the Pierson’s 8-year-old sister, Madison, and 3-year-old brother, Wyatt.

The fire quickly spread throughout the two story home as it was under renovation. “They had removed all the sheet rock, plaster or whatever off the ceiling and in the hallway, so that was all exposed,” Alcox said. “That’s what made (the fire) move along a lot faster.”

It’s believed Pierson and the three children were all sleeping upstairs at the time, but were awakened by the fire. “(Tyra Pierson) was found on the floor…with the baby right beside her,” Alcox said. “The other two children had gotten downstairs…but apparently they just couldn’t stand the heat.”

Investigators the fire may’ve started about half-hour before firefighters arrived. The police officer who spotted the fire was unable to enter the home because of the intense heat and smoke. Alcox said there are no signs the home had smoke detectors.

“Now, they may’ve melted prior to the time we got there…but we did not encounter any and did not ask the owner if they had any. My suspicion is if there were smoke detectors, they were not working,” Alcox said. Madison and Wyatt’s parents, Tony Pierson and Kim Kraft, were both at work at the time of the fire.