(NEXSTAR) – A grandmother and and three elementary school-aged children died in a house fire Tuesday morning after their neighborhood lost power amid frigid temperatures, according to fire officials.

Doug Adolph, spokesman for Sugar Land Fire and EMS, told reporters that firefighters responding to a call around 2 a.m. found the Houston-area home already engulfed in flames. A responder had to physically stop a 41-year-old woman, identified as the mother of the children, from trying to run into the blaze to rescue her kids.

The cause of the fire is not yet clear, but social media photos showed the family using the fireplace for heat after the neighborhood lost power eight hours earlier, Adolph said.

The mother and a female friend both suffered burn injuries and were taken to an area hospital, Adolph said. He confirmed that the woman who died in the fire is the mother of the 41-year-old.

Millions lost power in Texas after the state’s electrical grid was overwhelmed by demand during a bitterly cold winter storm, leaving residents shivering in unheated homes as the temperature fell to single digits.

Houston authorities reported that a woman and an 8-year-old girl died of carbon monoxide poisoning after leaving a car running in the garage in an effort to stay warm.

Fire officials in Harris County, which includes Houston, said at least 14 people, including 7 children, have been transported to the hospital for carbon monoxide poisoning over the last 24 hours.