LOS ANGELES, California (CNN) -- More than 100 Los Angeles-area firefighters are battling a large fire on a back lot at Universal Studios, fire authorities said.
There were reports of an explosion in the studio's adjacent amusement park, said Los Angeles County Fire Capt. Frank Reynoso.
The three-alarm blaze damaged four or five structures, a fire official told reporters.
The fire began about 4:45 a.m. PT (7:45 a.m. ET) Sunday and reportedly damaged two "prop" buildings, including a chapel, and a popular ride called the "Cyclone," Reynoso said.
The theme park will open Sunday, though the studio tour will be affected by the blaze, according to Universal Studios spokesman Eliot Sekuler.
Television footage showed the blaze burning through the roofs of structures at the park and large plumes of smoke.
"It will be awhile before we have it under control," Reynoso said.Firefighters were dropping water on the blaze from helicopters.