FLORA, Ind. (AP) — Investigators say a central Indiana house fire that killed four young sisters started in the home’s kitchen, although its cause hasn’t been determined.

The Indiana Department of Homeland Security says Monday’s fire originated in the apartment house’s kitchen, possibly behind a refrigerator.

The investigation into the fire’s cause is ongoing.

The four girls succumbed to smoke inhalation, according to preliminary findings. Their mother and two law enforcement officers who tried to rescue the children were injured in the fire in the town of Flora, about 60 miles north of Indianapolis.

Flora police Officer Josh Disinger pulled Carroll County Sheriff’s Deputy Drew Yoder to safety after he was overcome by smoke during his rescue attempt.

WXIN-TV reports Yoder remains hospitalized but has written Disinger a thank-you note for saving his life.