So they've asked a security firm to use metal detectors and special night-vision glasses that can see in the dark to help them.
Should someone get a recording device past the metal detectors, then guards wearing the goggles would be able to spot them using it inside.
Some people try to sneak video cameras into cinemas
Film bosses are getting more and more annoyed because people are downloading films from the internet rather than paying to see them in the cinema.
A spokesman for the Motion Picture Association of America said the US film industry estimates it loses between £1.8bn and £2.4bn to online piracy every year.
Finding Nemo was made by Pixar, who uses computers to make animated films for Disney like Toy Story, Toy Story 2, A Bug's Life and Monsters, Inc.
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