by Kathy DiNuzzo and Biodun Iginla, BBC News, New York
Kim Kardashian, Vanessa Hudgens and Mary-Kate Olsen are some of the stars who appear to have been targeted.
It's thought to be the second massive hacking-related leak in less than a month, but it's not clear yet where the pictures came from.
They were briefly posted on 4chan and Reddit before being removed, according to reports.
Newsbeat has contacted the websites but hasn't had a response yet.
There's no word from any of them yet.
Kim Kardashian spoke to Newsbeat after the original iCloud hack at the start of September, saying: "'I think it's a big wake up call for people to make sure they have every privacy setting".
She added that people have to be "cautious" but claimed she didn't have an iCloud account on her phone.
At the time, Lawrence's agent told Newsbeat her team would be taking legal action.
The original list of mostly female stars affected also featured people like Rihanna, Kate Upton and Selena Gomez.
Reddit later shut down a forum called The Fappening, which became a destination for users wanting to see the pictures.
Apple called the first hack a "targeted attack" but denied its iCloud storage system had been compromised.
Celebrity blogger Perez Hilton said sorry for re-posting the original pictures earlier this month.
The FBI is already investigating the earlier breach.
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