Two of foster children, both teenage brothers, remain in stable condition after a house fire that police say may have been set on purpose, killing two of their foster siblings and the couple who has taken care of them for years.

A fire believed to be arson killed four family members, including two children, at a West Englewood home in Chicago early Wednesday morning, PEOPLE reports.

Chicago fire officials said the blaze involved a residential building, prompting a large emergency response with additional ambulances and personnel.