Fire officials say a fire on a back lot at Universal Studios has already destroyed several movie sets.
A Los Angeles county fire inspector says one building and at least three blocks of movie facades have burned, including mock New York and New England streets.
So far there are no reports of injuries.
Officials say the blaze started on a sound stage just before dawn. A thick column of smoke could be seen rising thousands of feet into the air. More than 100 firefighters have been trying to keep the flames from spreading to nearby brush.
A Universal Studios spokesman confirms that filming was going on when the fire broke out, but had few other details.
Some of the more familiar sights on the back lot include the clock tower from the "Back To The Future" movies and the house featured in "Psycho."