"The King Kong exhibit is three quarters lost," Inspector Rick Garrido of the Los Angeles County Fire department told PEOPLE Sunday. "The New York set has been totally lost."
Right now the fire is contained to a single structure, and they expect to have it under control within an hour. "Universal City Walk and Studios is open," he said "Only the backlot is closed."
Universal Studios is also the scene of Sunday's MTV Movie Awards. MTV tells PEOPLE the show will go on as planned.
Los Angeles County Fire Inspector Daryl Jacobs said at least one building had burned and as many as three blocks of movie facades were destroyed. "The facades are constructed of heavy timber and they tend to burn quite freely," he said.
Investigators have not yet determined the cause of the fire, which broke out just before dawn on a sound stage, fire Capt. Frank Reynoso said, adding that more than 100 firefighters were trying to prevent the flames from spreading to nearby brush and there was at least one explosion.
Recent films and TV shows that have used the now lost "New York Street" set are Spiderman 2, The Transformers, Ghost Whisperer, and Crossing Jordan.
Universal Studios spokesman Elliot Sekuler said the theme park would open Sunday, though the studio tour would be affected by the blaze.
Some of the more familiar attractions on the backlot are the clock tower from the Back To The Future movies and the house featured in Psycho.
Reporting by OLIVER JONES
Andrew Gombert / Reuters / Landov