I would wait for a report as to what caused the bathroom linen closet to catch on fire? Electrical issue? Storage of flammable product? Just keep in communication with the tenant. Letting the T know as soon as the cause of the fire is known. Then you will be able to settle with any rent or deposit. If your insurance covers complete re-build , then I would most prorate the rent and return the security. Depending on what the report states. If the fault was electrical then on you. If a candle left burning, then on the T.