CORPUS CHRISTI - Fire investigators have determined the Stonewall Post Office in Annaville is unstable due the damage caused by the fire Tuesday night.
At this time it is unclear if the building will be torn down.
But investigators have narrowed the source of the fire to a wall socket where a heater and paper shredder were plugged in.
Post office officials say about 3,000 pieces of mail were damaged and some mail may smell of smoke because of the fire.
We're told postal workers have been moved to other locations for the time being and are working to make sure everyone gets their mail.