Apple said Monday it was “actively investigating” the violation of several of its iCloud accounts, in which revealing photos and videos of prominent Hollywood actresses were taken and posted all over the Web.

“We take user privacy very seriously and are actively investigating this report,” said Apple spokeswoman Natalie Kerris.

Photos, some real, some said to be fakes, are said to have been taken from the iCloud accounts of several celebrities, such as actress Jennifer Lawrence. They were posted to the Web image-sharing community 4Chan and have since spread across the Web, showing up on social media sites like Twitter, Reddit and elsewhere.

Security experts said the hacking and theft of revealing pictures from the Apple iCloud accounts of a few celebrities might have been prevented if those affected had enabled two-factor authentication on their accounts.

More: Apple Says It Is ‘Actively Investigating’ Celeb Photo Hack