SOUTH JORDAN, Utah, Oct. 28 (UPI) -- A South Jordan, Utah, movie theater said patrons attending the opening of Disney's "High School Musical 3" were instead briefly shown a sexually explicit film.

Managers at the Megaplex Theatre said they switched a showing of the G-rated Disney musical film Friday night to a larger auditorium but they forgot to switch out the reel of the previous film, the R-rated "Sex Drive," the Deseret Morning News reported Tuesday.

Patrons said the opening moments of the film included nudity.

"I could not carry my little children out before they were exposed to extremely vulgar and sexually explicit material," one parent said after the screening, the report said.

Managers at the theater said they apologized to the audience and distributed free movie vouchers and concession coupons.

Megaplex spokesman Jeff Whipple said greater supervision will be given to employees charged with switching reels in the future to prevent further occurrences.