The GTA series is one of the world's most popular games

The scenes in Grand Theft Auto: San Andreas, the best-selling game of 2004, were unlocked by a fan who created software called Hot Coffee.

Installing Hot Coffee allowed people to play an explicit "mini game".

As a result, the US Entertainment Software Rating Board (ESRB) changed the rating to Adults Only.

The change meant, however, that many shops were forced to stop stocking it as they have a policy of not selling adult-rated content.

In Australia, the game was stripped of its official classification, meaning that shops could no longer sell the title.

"The Hot Coffee scenes were not intended to be part of the Grand Theft Auto: San Andreas experience," read a statement from the Rockstar, the game's developer.

"If your copy of Grand Theft Auto: San Andreas for the PC has been altered by the unauthorised Hot Coffee download circulating on the internet, or you wish to prevent your version from being so altered, download and install the patch for your version of the game."

From the start

Before the ESRB's investigation, the game had an M for mature rating that meant it could be sold to those aged 17 and above.

GTA: San Andreas has sold millions worldwide

It later admitted it had created the secret scenes, following the ESRB investigation.

The storm of protest over the game even attracted the attention of US senator Hillary Clinton.

She called for an investigation into who was responsible for including the scenes in the game.

In the UK, the game was originally granted an 18 age rating and that rating remains the same.