Just an update: The fire was due to a faulty Frigidaire clothes dryer. The inspector said it was the second or third one in a few weeks that he saw cause a fire. Check your appliances all.
My brother and his family are now back in the house, but only on certain floors. They've had four to six specialists there everyday cleaning, using exhaust fans, etc. They're now looking for painters, carpenters, and electricians to start the hard work.