The Oct. 10 blaze, which began in a ground-floor office of the animator's Victorian warehouse in Bristol, resulted from an electrical fault in an appliance, they said.
Hundreds of sets, props and models from the company's animated clay films were destroyed in the fire, including sets from "A Grand Day Out," "The Wrong Trousers" and "A Close Shave," the short films that introduced eccentric inventor Wallace and his unflappable dog Gromit.
Sets and props from Wallace & Gromit's feature-length debut, "Curse of the Were-Rabbit," were not caught in the blaze.
The appliance that sparked the fire, said assistant chief fire officer Bill Feeley, was either a camera monitor or a water heater.
He said the devastation could have been avoided if the building had been equipped with a sprinkler system.