LOS ANGELES — Low water pressure hampered efforts Sunday to fight a fire that raged through the Universal Studios back lot in Universal City, destroying a soundstage and several sets, including the Courthouse Square seen in “Back to the Future” and the New York street scene from the 1987 “Dragnet” film and “Bruce Almighty,” as well as structures used in the theme park’s King Kong attraction.

As the equivalent of two city blocks burned, and firefighters were still knocking down flames seven hours after the blaze began, a mushroomlike cloud of smoke drifted over surrounding neighborhoods, raising some health concerns. Nevertheless, the studio theme park was scheduled to reopen in the afternoon.

“We certainly hope we will be able to open … and give our guests a day of entertainment,” said Universal spokesman Eliot Sekuler. About 25,000 people visit the park on a normal weekend day.

Air-quality officials said they had not been notified of any hazard.

“As far as I know, we have not been asked our opinion on whether or not the park should reopen,” said Sam Atwood, spokes- man for the Air Quality Management District. “I don’t think we have the power or the authority to do that.”

Atwood said that if they were asked to take samples, the soonest results could be completed would be by this evening.

One known air-pollution risk from the motion-picture industry is perchloroethylene, otherwise known as “perc.” The substance, which has been linked in studies to cancer, was used for cleaning film until the AQMD adopted a regulation to limit its use and replace it with less toxic cleansers. Richard Drury, an environmental attorney, who has clashed with the AQMD on pollution issues, disagreed on the agency’s role in the Universal fire and said cheap plastics used at most industrial locations were also a worry.

“They certainly have jurisdiction here,” he said. “Any time you’re burning plastic, firefighters are always concerned.”

But Drury said it was important not to overstate the risks, noting short-term exposure to carcinogens, for instance, might not pose a threat: “One-time exposure is probably not that significant.”

At least 300 firefighters battled the blaze, including with water-dropping helicopters. The fire, which started at about 4:30 a.m. local time, was expected to burn into the afternoon, although it was contained. Four firefighters suffered minor injuries.

The flames tore through a cavernous, two-story video vault containing video and copies of film, some dating to the 1920s. At one point, firefighters hastily removed canisters from the building by hand, but Universal officials said that the archives were copies, and no original works had been lost.

Los Angeles County Fire Chief P. Michael Freeman said the park had installed a large-scale sprinkler system after a 1990 blaze, but it didn’t seem to work adequately. Firefighters pulled water from ponds and lakes on the back lot. They also brought in a 6,000-gallon water tender.

“It appears the fire this morning overwhelmed fire protection features,” he said. “We’re going to readily and quickly reevaluate that and see if that had any impact on the water pressure.”

The spectacular 1990 blaze ravaged more than four acres of the back lot, destroying many of the same sets that burned this time. It also burned the “Dick Tracy” building and the “Ben Hur” set.

The giant column of black smoke from the fire could be seen for miles. Officials said the fire was able to spread so fast in part because the studio sets were made of timber.

“Big lumber causes a big fire,” said county Fire Inspector Daryl Jacobs, noting that some of the soundstages date to the 1930s and ’40s.

Movie scenery destroyed

Two of Universal Studios’ iconic back lot sets, where some of Hollywood’s memorable movie moments were filmed, were destroyed in a fire Sunday.

Courthouse Square:

“Inherit the Wind” (1960)

“To Kill a Mockingbird” (1962)

“Back to the Future” trilogy (1985, 1989, 1990)

“Amistad” (1997)

“Bruce Almighty” (2003)

New York Street:

“Dirty Harry” (1971)

“The Sting” (1973)

“Earthquake” (1974)

“The Blues Brothers” (1980)

“Streets of Fire” (1984)

“Austin Powers” (1997, 1999)

“Transformers” (2007)