Aardman said an early morning fire on Monday gutted its warehouse in this western English city, destroying a priceless archive of props, sets and models.
Aardman had just learned that "The Curse of the Were-Rabbit," the first full-length adventure for the eccentric inventor and his indomitable dog, hadon its opening weekend.
"Today was supposed to be a day of celebration, with the news that Wallace and Gromit had gone in at number one at the U.S. box office, but instead our whole history has been wiped out," said Aardman spokesman Arthur Sheriff. "It's turned out to be a terrible day."
The Avon Fire and Rescue service said the roof and three interior walls of the Victorian warehouse collapsed in the blaze, which broke out at about 5:30 a.m. The cause of the fire was being investigated.
Sheriff said the warehouse contained sets, props and models from all the company's past productions, from the children's cartoon character "Morph" through the Oscar-winning, anthropomorphic "Creature Comforts" series to the Wallace and Gromit films.
Aardman said the sets and props from "Curse of the Were-Rabbit" were not caught in the blaze.
Wallace and Gromit's creator, Nick Park, said the earthquake in South Asia helped put the loss into perspective.
"Even though it is a precious and nostalgic collection and valuable to the company, in light of other tragedies, today isn't a big deal," he said.
Founded in 1972, Aardman is closely associated with animator Park, who joined in 1986, fresh out of film school.
Park used stop-motion clay animation to create cheese-loving inventor Wallace and his mute but resourceful dog Gromit. They starred in three shorts — "A Grand Day Out" (1989), "The Wrong Trousers" (1993) and "A Close Shave" (1995). The latter two won Academy Awards.
Park and Aardman's Peter Lord also directed the 2000 feature "Chicken Run," which spoofed the World War II prison-camp classic "The Great Escape" with a cast of clay poultry.
"Wallace & Gromit: The Curse of the Were-Rabbit" opened in the United States on Friday and took $16.1 million at the box office over the weekend. It opens in Britain Oct. 14.