HOUSTON (AP) — Three young children and their grandmother died in a Houston-area house fire early Tuesday morning while it’s believed they were trying to stay warm during a power outage, according to a fire official.

Sugar Land Fire and EMS spokesman Doug Adolph said that when firefighters arrived after the call at about 2 a.m., the house was fully engulfed and the 41-year-old mother of the children and her female friend were outside of the home and suffering from burns. He said a responder had to restrain the mother from going back into the house.

Both women have been taken to a hospital.

He said they are still investigating the cause of the fire but that the neighborhood had been without power for over eight hours and social media posts from the family indicated they were using the fireplace to keep warm.

He did not have ages for the children but said they were elementary school aged. He said their mother was the daughter of the woman who died.