Apple has shut down Facebook’s ability to distribute internal iOS apps, from early releases of the Facebook app to basic tools like a lunch menu. A person familiar with the situation tells The Verge that early versions of Facebook, Instagram, Messenger, and other pre-release “dogfood” (beta) apps have stopped working, as have other employee apps, like one for transportation. Facebook is treating this as a critical problem internally, we’re told, as the affected apps simply don’t launch on employees’ phones anymore.

The shutdown comes in response to news that Facebook has been using Apple’s program for internal app distribution to track teenage customers with a “research” app.

“A clear breach of [Facebook’s] agreement with Apple”

That app, revealed yesterday by TechCrunch, was distributed outside of the App Store using Apple’s enterprise program, which allows developers to use special certificates to install more powerful apps onto iPhones. Those apps are only supposed to be used by a company’s employees, however, and Facebook had been distributing its tracking app to customers. Facebook later said it would shut down the app.

This poses a huge issue for Facebook. While Apple provides other tools a company can use to install apps internally, Apple’s enterprise program is the main solution for widely distributing internal apps and services. In an email, a Facebook spokesperson said “I can confirm that this affects our internal apps.”

In a statement given to Recode, Apple said that Facebook was in “clear breach of their agreement with Apple.” Any developer that breaches that agreement, Apple said, has their distribution certificates revoked, “which is what we did in this case to protect our users and their data.” Apple declined to comment on shutting down all of Facebook’s internal apps in an email to The Verge.

Revoking a certificate not only stops apps from being distributed on iOS, but it also stops apps from working. And because internal apps by the same organization or developer may be connected to a single certificate, it can lead to immense headaches like the one Facebook now finds itself in where a multitude of internal apps have been shut down.

Apple and Facebook have already been bickering over privacy, but this is the first instance of Apple taking an action that directly shuts down some of Facebook’s activities. Last March, Apple CEO Tim Cook criticized Facebook’s handling of the Cambridge Analytica data sharing scandal, saying, “I wouldn’t be in this situation” if he were running the company. Facebook CEO Mark Zuckerberg later said the comments were “extremely glib” and spoke of Apple as a company that “work[s] hard to charge you more.”

Update January 30th, 2:17PM ET: Facebook confirmed that its internal apps are affected by Apple revoking its enterprise certificate.