Selena Gomez is allegedly among the dozens of victims of a massive celebrity hacking that includes intimate photos of many of Hollywood’s biggest stars.

Naked images purporting to be of many of the stars began appearing online on Sunday, although the authenticity of many of the images could not be confirmed. The source of the leak was unclear.

The FBI says it is addressing allegations that nude photos were stolen and posted online.

A statement released by the agency Monday afternoon doesn't elaborate on what steps are being taken to determine how intimate images of Oscar-winning actress Jennifer Lawrence and other stars were leaked.

The photos of Lawrence and others began appearing online Sunday. The 24-year-old's publicist called the release of the images a violation of the actress's privacy.

Apple said Monday it is investigating whether any of its customers' iCloud accounts had been tampered with.

Earlier in the day, Lawrence, the actress who stars in “The Hunger Games” film franchise, contacted authorities to ask them to investigate who stole and posted nude images of the Oscar winner online, a publicist for the actress said.

Intimate images of Lawrence appeared over the weekend. Some showed her fully nude.

Others whose photos purportedly have been posted online in the hacking effort are singer Rihanna, actress Kaley Cuoco, who stars in the television hit “The Big Bang Theory,” model Kate Upton, actress Kirsten Dunst and actress/singer Vanessa Hudgens.

Some stars, or their representatives, have posted messages saying that the photos that supposedly are of them are actually fake. Others, though, essentially admitted that the photos are authentic and have demanded they be removed.

The photos were allegedly discovered by an iCloud leak that allowed the stars’ telephones to be hacked, according to published reports. Some photos first appeared on the image-sharing site 4chan.

"This is a flagrant violation of privacy," Lawrence's publicist Liz Mahoney wrote in a statement. "The authorities have been contacted and will prosecute anyone who posts the stolen photos of Jennifer Lawrence."

Mahoney declined to provide further details, including which authorities were contacted.

Lawrence, 24, is a three-time Oscar nominee.

Celebrity blogger Perez Hilton initially put some of the controversial pictures on his website, but then removed them and apologized for having posted them.

"I acted in haste just to get the post up and didn't really think things through," Perez said. "I'm sorry. At work we often have to make quick decisions. I made a really bad one today and then made it worse. I feel awful and am truly sorry."

The FBI has investigated previous leaks of nude celebrity images, including leaks involving Scarlett Johansson, Mila Kunis, Christina Aguilera and footage of television sports reporter Erin Andrews in a Tennessee hotel room. Those cases resulted in convictions.

How widespread the hacking of celebrities photos was is not immediately clear.

Some cybersecurity experts speculated that hackers may have obtained a cache of private celebrity images by exploiting weaknesses in an online image-storing platform.

"It is important for celebrities and the general public to remember that images and data no longer just reside on the device that captured it," security researcher Ken Westin wrote in a blog post Monday. 

"Once images and other data are uploaded to the cloud, it becomes much more difficult to control who has access to it, even if we think it is private."

Private information and images of celebrities are frequent targets for hackers. Last year, a site posted credit reports, Social Security numbers and other financial info on celebrities, including Jay Z and his wife Beyonce, Mel Gibson, Ashton Kutcher and many others.

Johansson, Kunis and Aguilera were hacked by a Florida man, Christopher Chaney, who used publicly available information to hack into the email accounts of more than 50 people in the entertainment industry.

"I have been truly humiliated and embarrassed," Johansson said in a tearful videotaped statement played in court at Chaney's sentencing in December 2012.

"That feeling of security can never be given back and there is no compensation that can restore the feeling one has from such a large invasion of privacy," Aguilera wrote in a statement before Chaney's sentencing.

The Associated Press contributed to this report.

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