Paramount Studios in Hollywood has been locked down after police shot at a suspect, who has since barricaded himself inside a building.
There were unconfirmed reports that a man was armed with a knife at the site, where there was a huge police presence late Sunday night.
A spokesperson for the Los Angeles Police Department (LAPD) told local media that shots were fired by the force.
Police were called to the scene after reports about a man on the lot, and at some point police opened fire and the suspect ran off, CBS Los Angeles reported.
It is said that the suspect was barricaded inside a building and a heavily-armed SWAT team was called in.
Police were using a sniffer dog to search buildings on the lot.
A helicopter was flying overhead and shining a light on the site.
Officers swarmed the film studio's lot at about 10pm local time.
Photojournalist John Schreiber, who was over the scene in a helicopter, said police appeared to be focusing on the Washington Square backlot, which recreates the park in New York.
The LAPD tweeted: "There is currently heavy police activity within our @LAPDHollywood Division in the vicinity of the 5500 block of Melrose Ave.
"If you live in the area, please stay indoors.
"If you don’t live in the area, please stay away at this time."
The LAPD Hollywood Division added: "Police activity in the area of Melrose/Gower. Avoid the area."
