Fire in rental

I Have a rental house which had new carpet, new blinds, redone bath. The whole house was newly painted and clean.
The tenants have been renting for 11/2 years.
Do I have to return the deposit back if the fire was caused by their extension cord which was hooked up to the battery charger and A/C they bought and installed in the window.
The fire inspector found the electrical outlet in pristine condition and comfirmed that it was the cord which was under the sofa ( possibly rubbed portions of the cord) to create a short and thereby created heat which started fire.
Fire damages may be up to $75,000.

I have landlords insurance with a $1000.00 deductable.
I know after the fire and I get damages repaired my insurance rates will go up with the possibility of cancellation because of their accident of negligence.
I know that my clean record on my CLUE and A-Plus will have a black mark which may put me in high risk status to get insurance.

Please direct me,
Maria

I would say you have a legitimate claim to the deposit if everything you mentioned is in fact the way it went down. They will probably sue you for the $$$ but you would then produce all evidence in court.