YouTube is under scrutiny again for failing to catch objectionable content.

The Google-owned video site apologized on Thursday for running ads from major brands against fake medical news and AIDS denial content. The brands included Mercedes Benz, Toyota and Wix, a platform that helps people create websites, according to Adweek.

The videos included assertions that HIV infections aren’t dangerous and that HIV doesn’t lead to AIDS, Adweek reported. YouTube has stopped running ads against the videos.

A YouTube spokesman acknowledged its filters hadn’t caught the videos and apologized for the incident. 

“We immediately removed ads on violating videos and credited advertisers,” a YouTube spokesman said in a statement. “While our system and controls work as intended 99% of the time, there are a small number of instances where they do not and we are committed to closing that gap even further.”

The company said the videos had very little reach and earned less than $100 in total over the last two months.

Representatives from Mercedes, Toyota and Wix didn’t immediately return requests for comment.

The controversy comes as giant tech companies grapple with how to deal with content on their platforms. 

YouTube has said it was adding 10,000 human moderators to its team for flagging content. The company also uses software and machine learning to flag inappropriate content. 

Facebook has been scrutinized for misinformation and toxic content on its platform too. In response, CEO Mark Zuckerberg has said he’s adding 20,000 moderators to the social network’s security teams.

Last year, YouTube faced an advertiser boycott after its automated technology ran ads against extremist videos, including one that featured former Ku Klux Klan leader David Duke. The British government, AT&T and Johnson & Johnson were among advertisers that ditched the platform. 

Google CFO Ruth Porat later said that most of the advertisers that left YouTube eventually returned.

YouTube also drew controversy last year for inappropriate videos on YouTube Kids, a version of the site that’s meant to be child friendly. The service’s filters failed to recognize or remove some videos that featured disturbing imagery but were aimed at children. The images included Mickey Mouse lying in a pool of blood and a claymation version of Spider Man urinating on Elsa, the Disney princess from “Frozen.”

The company responded by updating its policies to include blocking of inappropriate comments on videos featuring minors and providing guidance for creators who make family-friendly content.

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