Who put the sex in "Grand Theft Auto"? That's the question buzzing in video-game circles.

For years, the hottest franchise in video games has been under fire for its depiction of violence against police, prostitutes and various ethnic groups. Now come complaints that sex scenes possibly hidden in the series' latest installment, "Grand Theft Auto: San Andreas" (which is already rated "M" -- intended for players aged 17 and up -- by the Entertainment Software Ratings Board), should be given the video-game equivalent of an X rating.

"Once again, ESRB has failed our parents," California Assemblymember Leland Yee said in a statement released last week. "This particular game has been known to include extremely heinous acts of violence, and now it has been uncovered that the game also includes explicit sexual scenes that are inappropriate for our children. I have urged the ESRB on numerous occasions to rate this game AO ['adults-only'] based on its blatantly graphic nature."

In a statement released Friday, the National Institute on Media and the Family echoed the call for a switch to an AO rating. Such a move would position "GTA" in an unusual spot. Many retailers will not stock AO games, which has chilled major publishers' enthusiasm for making them. The ESRB ratings database lists more than 600 M-rated games; for the AO rating, the number of games is 18.

But the question in video-game circles for the past month hasn't been whether "GTA" deserves an AO rating because of its content, but whether the controversial content is actually in the game.

Those in the best position to know -- the game's developers -- declined a request for an interview about the subject but issued a statement saying that the hidden sex scenes "are not represented or playable" in the retail version of the game. The company did not address specific questions about whether the scenes were hidden, intentionally or accidentally, on "GTA" discs that made it to stores -- and they certainly are "playable," because many gamers have found ways to play them.

The controversy began in early June, when a Dutch gamer named Patrick Wildenborg released the "Hot Coffee Mod," a downloadable application that introduced a startling new element to the PC version of "San Andreas": interactive sex.

The game, which was initially released on PS2 in October 2004 but is now also available on PC and Xbox, always allowed the player-controlled protagonist, CJ, to date a variety of women in the sprawling state of "San Andreas." The dates involved activities typical of the franchise's satirical bent. For example, one hard-nosed girlfriend would request that her nights out consist of drive-by shootings. If players could get their hero to sufficiently charm one these girlfriends, CJ would be invited into a girlfriend's house for "hot coffee." At that point, the game's camera would remain outside the girlfriend's house, but the muffled noises emanating from within the digital domicile left no doubt about what the "coffee" really meant.

Events would play out differently with Wildenborg's "mod." The programming tweak required some manipulation of the game's source code. That kind of under-the-hood tweak requires more tech savvy than the standard video-game bonus, which might reward a player with infinite lives if they can strike the proper 12-button combination on their controller.

Once "Hot Coffee" was properly activated, an invitation for coffee would lead to an interior view of CJ and girlfriend in the bedroom indulging in their affections, according to Internet reviews by people who successfully ran Wildenborg's programming trick. More than a non-interactive cut-scene, the couple's copulation would play out as a controllable mini-game. Button presses affected performance.

However, downloaders noticed that a few things didn't seem quite right. CJ remained clothed, making the action onscreen anatomically improbable. And the mini-game was difficult to control, suggesting amateurish or unfinished programming.

The question arose as to whether Wildenborg had crudely created a new bit of gameplay, or whether he had unearthed unfinished code that had been abandoned by the game's developers and left on the game's disc. If Wildenborg had simply created new content, then he was following in the long tradition of "modding" games, creating new content based on established code in a way similar to how fans modified the code of the hit first-person shooter "Half-Life" into a whole new game, "Counter-Strike," which itself became a hit game.

Wildenborg said he hadn't created that kind of mod. On his Web site, he wrote: "All the contents of this mod were already available on the original disks. Therefore the script code, the models, the animations and the dialogs by the original voice actors were all created by Rockstar. The only thing I had to do to enable the mini-games was toggle a single bit in the main.scm file." In other words, Wildenborg claimed that he had simply found a key that unlocked a Rockstar-programmed secret.

In an e-mail interview with MTV News on Monday (July 11), Wildenborg said the mod came about when "some fellow modder discovered the animation sequences somewhere on the PS2 disc while browsing through its data files." That revelation means that the code would have been buried in 2004's PlayStation 2 version. "At first we thought these were just the regular 'leftovers' from old gameplay ideas that had not been finished. But after further investigation with home-brewed tooling, I slowly discovered what emerged as a complete mini-game. But it was very carefully removed from the normal gameplay -- to the best of my knowledge, all this stuff is under no circumstance playable on an original installation of the game. We were, however, able to craft a 'software-key' that unlocks this content."

It wouldn't have been unprecedented for a game developer to have left content on retail copies of the disc that it didn't intend for gamers to access. Hackers have found cutting-room-floor content buried in games such as "GoldenEye." Rockstar, however, isn't saying if this is the case. In a statement, the company said: "The scenes depicted in the 'Hot Coffee' modification are not represented or playable in the final version of the game available at any retail outlets. The 'Hot Coffee' scenes cannot be created without intentional and significant technical modifications to the PC version of the game's source code."

This wouldn't be the first time Rockstar had left scuttled code in a "GTA" game, said Jordan Liles, site director for planetgrandtheftauto.com. According to Liles, code sleuths have also found graphics for a skateboard in "San Andreas," even though no skateboard is usable in the game. He added that the game also included leftover images from "Grand Theft Auto: Vice City," and the PC version of the single-player "GTAIII" even included some rough options for a multi-player mode -- all tucked away and inaccessible to regular users of the games.

A Rockstar representative did confirm that the ESRB is conducting an investigation, and the company said in a statement that "we also feel confident that the investigation will uphold the original rating of the game, as the work of the mod community is beyond the scope of either publishers or the ESRB."

Representatives from the ESRB did not return a request for an update about the investigation by press time. Over the weekend, ESRB president Patricia Vance told the Boston Globe that "Hot Coffee" mini-games would likely not affect the game's ratings, because they were not available to users unless they meddled with the game's source code. But, she added, the incident "raises issues about what's considered playable content." She asked, "Should there be complete disclosure of non-playable content?"

For now, "GTA" is still available on store shelves with an M rating. According to the game's box, the game is rated M for blood and gore, intense violence, strong language, strong sexual content and use of drugs.