MTV executives have a new hit drama on their hands, featuring the sexual and drug-fueled exploits of misfit teenagers. They also have something else -- a fear that coming episodes of the show may break the law.

In recent days, executives at the cable channel became concerned that some scenes from the provocative new show "Skins" may violate federal child pornography statutes. A parents group and others have complained about the show and called for a federal investigation.

MTV executives ordered the producers to make changes to tone down some of the most explicit content.

The executives are particularly concerned about the third episode of the series, which is to be broadcast Jan. 31.

In an early version, a naked 17-year-old actor is shown from behind as he runs down a street. The actor, Jesse Carere, plays Chris, a high school student whose erection -- assisted by erectile dysfunction pills -- is a punchline throughout the episode.

The channel intends for the editing to obscure some of the sexual content in the third episode and others.

The planned changes indicate that MTV, which has been pushing the envelope for decades, may be concerned it pushed too far this time.

"Skins" is a calculated risk by MTV, a unit of Viacom, which is eager to get into the scripted programming business. The channel has long tested U.S. standards for sexuality and obscenity on television with shows like "The Real World" and "Jersey Shore."

Those reality shows have generally involved adults, but for "Skins," the producers purposefully cast actors ages 15-19, most of whom had never acted before.

MTV's president and other executives have declined interview requests. An MTV spokeswoman, Jeannie Kedas, insisted that the future episodes of "Skins" were still works in progress. She would not confirm that MTV executives were fearful of running afoul of child pornography laws.

"'Skins' is a show that addresses real-world issues confronting teens in a frank way," she said in a statement. "We review all of our shows and work with all of our producers on an ongoing basis to ensure our shows comply with laws and community standards. We are confident that the episodes of 'Skins' will not only comply with all applicable legal requirements, but also with our responsibilities to our viewers."

Child pornography is defined by the United States as any visual depiction of a minor engaged in sexually explicit conduct. In some cases, "a picture of a naked child may constitute illegal child pornography if it is sufficiently sexually suggestive," according to the Justice Department's legal guidance. Anyone younger than 18 is considered to be a minor.

The youngest cast member on "Skins" is 15.

"Skins" is an import from Britain, a country that in contrast with the U.S. has historically displayed a higher tolerance for TV eroticism. Episodes there included simulated masturbation, implied sexual assault, and teenagers disrobing and getting into bed together. The early episodes for MTV, including the third one, are virtually identical to the source material.

With ads that feature groups of barely clothed teenagers, "Skins" is surely one of the most sexually charged programs that the channel has featured. Before it even had its premiere, the Parents Television Council, a TV watchdog group, labeled "Skins" the "most dangerous program that has ever been foisted on your children." The group objected to the gratuitous scenes of drug and alcohol use, violence and sexual acts by high school-age children.

Earlier this week, one of the show's major advertisers, Taco Bell, pulled its ads from the show over the racy content.

Of course, that content may be what attracts young viewers. Jessica Bennett, a senior writer for Newsweek, wrote last week, "'Skins' may be the most realistic show on television."

The show is off to a running start. It attracted 3.3 million to its premiere on Monday night. Of those, 2.7 million were 12-34 years old, making "Skins" the most watched new show in the channel's history in that group.

Episodes of "Skins" are rated TV-MA, indicating that the content may be unsuitable for viewers younger than 17. MTV states in news releases that it is "specifically designed to be viewed by adults." However, many of MTV's viewers are in middle and high school. According to the Nielsen Co., the first episode drew 1.2 million people younger than 18.

MTV noted that the episodes were being shown only at or after 10 p.m. Eastern, and said in the statement, "We also have taken numerous steps to alert viewers to the strong subject matter so that they can choose for themselves whether it is appropriate."

It is unclear when MTV first realized that the show may be vulnerable to child pornography charges. On Tuesday, a flurry of meetings took place at the network's headquarters in New York, according to an executive who attended some of the meetings and spoke only on the condition of anonymity. In one of the meetings, the executives wondered aloud who could possibly face criminal prosecution and jail time if the episodes were broadcast without changes.

Ensconced in the VIP perch at MTV's premiere party for the series in New York on Friday night, the actors huddled around one another and stared in awe at the youthful party that was under way -- while unable to partake in the free alcohol that was flowing in the 21-and-older area. By midnight, several of the actors appeared to have headed home with their parents.

Referring to the largely unknown actors, Bryan Elsley, an executive producer of "Skins," said in a letter to critics last month, "They're making the characters their own and demanding that their voices be heard."

Elsley and his producing partners did not respond to interview requests on Wednesday, but MTV executives were known to be worried about how the producers would react to the planned changes.

There are, of course, innumerable examples of youthful sexuality being packaged by the media. Amy Adler, a professor of law at New York University who specializes in free speech, art and pornography, pointed to the teenage singer Miley Cyrus' revealing photo shoots and the CW network's use of condemnations by the Parents Television Council of the risque drama "Gossip Girl" to promote the show.

"There are times when I look at mainstream culture and think it is skirting up against the edge of child pornography law," she said.