YouTube has begun purging the site of channels and videos it deems predatory or non-family friendly, resulting in some channels with millions of subscribers and views going dark.

In a statement on its official blog, Johanna Wright, VP of Product Management at YouTube, said the company has noticed “a growing trend around content on YouTube that attempts to pass as family-friendly, but is clearly not. While some of these videos may be suitable for adults, others are completely unacceptable, so we are working to remove them from YouTube.”

Wright’s note claimed the service had terminated over 50 channels and removed “thousands of videos” in the last week. It also has implemented age restrictions on certain content, making it available only to those over age 18. It will also apply machine-learning technology to seek out potentially objectionable content for faster human review.

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Executives at YouTube are not the only ones noticing the questionable content. Several major advertisers have pulled advertising on YouTube after learning of their ads running on pages favored by pedophiles and other unsavory characters, some of whom left hundreds of comments on videos of scantily-clad children.

Among the reported drop-outs: candy company Mars, which makes M&Ms and Snickers; Mondelez (Oreos, Cadbury); and Diageo (Guinness, Smirnoff vodka, and Johnnie Walker scotch. An investigation by the UK news service The Times is believed to have sparked the advertiser uproar, but online forums have been discussing the issue of questionable content on YouTube for some time.

“We are shocked and appalled to see that our adverts have appeared alongside such exploitative and inappropriate content,” said a statement from the headquarters of McLean, Virginia-based Mars to USA Today. “We have stringent guidelines and processes in place and are working with Google and our media buying agencies to understand what went wrong. Until we have confidence that appropriate safeguards are in place, we will not advertise on YouTube and Google.”

Not every channel purged is sexual in nature. Toy Freaks, a channel with more than 8.5 million subscribers, was dropped because it reportedly posted content intended to gross-out children. Dozens of other channels appealing to kids have gone dark, which some observers estimate may account for upwards of 20 billion combined views.

The YouTube blog post by Wright promised five steps, including tougher application of community guidelines set by the video service and faster response to complaints; removing ads from inappropriate videos targeting families; blocking inappropriate comments on videos featuring minors; providing more guidance to content creators; and partnering with so-called “experts” while “doubling the number of Trusted Flaggers we partner with in this area.”