Movies.com writer Christopher Campbell broke the news via Twitter, later revealing details of the additional footage.
The bonus scene apparently shows members of the superhero team sat around a table eating shawarma - a reference to a remark made by Iron Man towards the end of the movie. It lasts for roughly one minute and features no dialogue.
The Avengers' first post-credits scene, which was included in the overseas release, shows Marvel Comics villain Thanos being informed of Loki's failure by one of his henchmen.
Joss Whedon's superhero epic landed in UK cinemas on April 26, opening to £2.4 million in the territory. It also recorded the biggest worldwide superhero opening of all time, claiming the box office number one spot across all 39 of its opening territories.
The Avengers opens in US cinemas on May 4.
> Read Digital Spy's review of 'The Avengers'
Watch a trailer for The Avengers below: