A large fire raged on a back lot at Universal Studios on Sunday, devouring a set from “Back to the Future,” the theme park’s King Kong attraction, and a video vault containing more than 40,000 videos and reels.

Los Angeles County Fire Captain Frank Reynoso says the blaze broke out just before dawn Sunday on a back-lot stage at the 400-acre property. The fire has been contained.

Officials say the iconic courthouse square from “Back to the Future” has been destroyed, and the famous clocktower that enabled star Michael J. Fox’s character to time-travel has been damaged.

NBC Universal President and Chief Operating Officer Ron Meyer says 40,000 to 50,000 videos and reels were damaged in the video vault, but there are duplicates in a different location.

Los Angeles County Fire Inspector Daryl Jacobs said at least one building had burned and as many as three blocks of movie façades were destroyed.

Two mock New York and New England streets used for movie-making and tourist displays were “a total loss,” he said.

The blaze broke out just before dawn on a soundstage at the 400-acre property, Fire Capt. Reynoso said. There was at least one explosion.

A thick column of smoke rose thousands of feet into the air and for a time helicopters swept in to drop water.

More than 100 firefighters were trying to prevent the flames from spreading to nearby brush, Mr. Reynoso said. One firefighter was hospitalized for unspecified injuries.

Officials said the theme park would open Sunday, though the studio tour would not go to the King Kong part of the attraction. The cause of the fire is under investigation.