About 400 firefighters were on scene extinguishing the blaze Sunday afternoon.
Shortly after 2:30 p.m. Sunday, an explosion injured two personnel on scene.
In total, 10 personnel were moderately injured in the blaze. Four of the firefighters from the L.A. County Fire Dept., and five others from L.A. City Fire Dept., were injured, according to L.A. County Fire Inspector Ron Haralson. One L.A. County Sheriff's deputy was also injured.
There were various reports of the cause of the fire, but no confirmed information.
A commercial shoot was going on when the fire broke out, said Universal Studios Spokesman Eliot Sekuler. Universal Studios Hollywood and CityWalk announced Sunday the theme park would be closed for the remainder of the day.
Fire inspector Darryl Jacobs said that firefighters did encounter some explosions from flammable materials such as propane tanks upon their arrival.
According to firefighters, the following structures have been damaged and/or destroyed:
Roughly 40,000 to 50,000 videos and reels were in the video vault, but there are duplicates stored in a different location, said Ron Meyer, NBC Universal president and chief operating officer. Firefighters managed to recover hundreds of those titles from the vault.
The videos included every film that Universal has produced and footage from television series including "Miami Vice" and "I Love Lucy."
The iconic courthouse square from "Back to the Future" was also destroyed, Freeman said, and the famous clock tower that enabled Michael J. Fox's character to travel through time was damaged.
The King Kong structure reportedly caught fire from the roof and compromised several of the surrounding structures.
The park was supposed to reopen Sunday afternoon, but due to the conditions it remained closed to the public for the remainder of the day. On a typical weekend day about 25,000 people visit Universal Studios.
Hundreds of visitors waited outside the park gates Sunday morning, where acrid smoke lingered, providing an eerie backdrop. Fire officials didn't believe air quality would pose a health hazard to the public.
The fire did not affect the 2008 MTV Movie Awards, which was broadcast live Sunday night from the Gibson Amphitheatre in Universal City.
The cause of the fire is under investigation, and no initial damage estimates were given.
In 1990, a fire broke out on a Universal lot. During that event, Santa Ana winds were instrumental in the overwhelming damage done to the New York Street facades. That particular blaze was ruled as arson. The 1990 blaze resulted in more than $50 million in damage and required a major undertaking to rebuild each of the sets.
The cause of Sunday's fire at Universal Studios was not known.
The Associated Press and City News Service contributed to this report.