UNIVERSAL CITY, Calif. (AP) _ A security guard was arrested today on suspicion of torching the historic Universal Studios backlot where Warren Beatty flirted with Madonna in ''Dick Tracy.''

Michael J. Huston, 40, of Tujunga was booked for investigation of arson and held in lieu of $1 million bail in the multimillion-dollar fire, said Deputy Rich Erickson of the Los Angeles County Sheriff's Department.

''He was on duty when the fire started and after questioning he was arrested early today at the studio,'' the deputy said. ''We won't disclose a possible motive.''

Huston is an employee of Burns International Security Services, which is under contract by Universal. He had been on the job one month, said Dan Slusser, general manager of Universal City Studios.

The John Landis movie ''Oscar,'' a production of the Walt Disney Co. and starring actor Sylvester Stallone, was the only film shooting on the backlot at the time of the fire, said Slusser. Actual filming had stopped for the day before the fire began and Stallone was not present.

''We lost the entire set and are going to shut down for a week to 10 days. We have to build New York Street somewhere,'' said ''Oscar'' publicist Spooky Stevens. ''We also lost 21 vintage cars, the camera equipment, props, every bit of wardrobe.''

The blaze damaged the studio tour's King Kong attraction, which features a 37-foot mechanical gorilla that appears to shake tramloads of tourists.

Hundreds of firefighters backed by water-dropping helicopters put out the windblown flames about three hours after the fire broke out at the 420-acre studio, Hollywood's biggest and longest-running movie factory. Universal Studios is visited by millions of tourists each year.

''It roared through the sets like a wildfire. It's like a blowtorch when the wind pushes the fire up against these structures,'' said Los Angeles County Battalion Chief Al Bennett.

Most of the damage was to the sunbaked wooden facades along the route of the studio tour, the third most popular tourist attraction in the nation.

''A lot of the streets are pretty well destroyed and are going to have to be rebuilt,'' Bennett said.

Among outdoor sets destroyed or damaged were New York Street, where parts of ''The Sting'' were filmed, Brownstone Street, and Courthouse Square, where Michael J. Fox rode his jet-powered skateboard in ''Back to the Future Part II.'' The ''Dick Tracy'' set also was gutted, county fire inspector Jim Gandee said.

But it was ''business as usual'' today with the first tour tram leaving on schedule at 9:30 a.m., said studio publicist Joan Bullard. She said about 20 percent of the 420-acre property was burned and estimated damage in the hundreds of millions of dollars.

''We are extremely disappointed to have lost history,'' Bullard said.

But she said only one ''attraction,'' or amusement-park-like feature of the tour, was damaged - King Kong. ''The mechanical part of that works, but there was water damage and we are checking the structural integrity of the building,'' Bullard said.

Fire officials said the earthquake ride also was damaged, but it worked normally today.

The cause of the fire was not immediately known. One firefighter was slightly injured.

Studio executives toured the $630 million theme park today to assess the damage.

''Everything looked like charcoal briquets,'' said Rusty Gilligan, who lives near the back lot. ''It was just a wreck.''

The flames, fanned by winds gusting up to 50 mph, were doused as they crept up to two film vaults. The Universal film library, which includes ''E.T. The Extra-Terrestrial,'' ''Jaws'' and ''Twins,'' is worth hundreds of millions.

The film library is vital to acquisition talks between Matsushita Electrical Industrial Co. and MCA Inc., Universal's parent. Matsushita has been discussing a multibillion-dollar buyout of MCA for several months.

The studio nestled in the Hollywood Hills 10 miles from downtown Los Angeles features a seven-hour journey through the backlot and includes a guided tram tour that takes viewers into sets and a simulated earthquake.

About 200 Universal employees and about 160 people at two restaurants on the studio grounds were evacuated after the fire broke out at 7:18 p.m.

''We really had a fire storm. ... It's a miracle that some firefighters didn't get seriously hurt,'' Freeman said.

At the nearby Universal Hilton, where the Californian Republican party had its election night headquarters, traffic tie-ups caused by the fire prevented some GOP supporters from reaching the hotel.

The fire is not the first to strike Universal. In 1987, a stage used for the 1959 epic ''Spartacus'' erupted in flames. Damage was put at $2.5 million.

Universal Studios, founded by Carl Laemmle, opened in 1915. It did not gain recognition until the 1920s, when it produced several now-classic silent films, including ''The Phantom of the Opera,'' and ''The Hunchback of Notre Dame.''

Universal is also home to such film classics as ''Psycho,'' ''Jaws,'' ''Out of Africa'' and ''To Kill A Mockingbird.''

Current TV shows shot at Universal include ''Major Dad,'' ''Murder She Wrote,'' ''Coach,'' ''Quantum Leap,'' ''Lassie'' and ''Matlock.''