During joint meeting of the Senate Commerce and Judiciary Committees earlier today, Facebook CEO Mark Zuckerberg told Vermont Senator Patrick Leahy that people at Facebook had been contacted by special counsel Robert Mueller.

Zuckerberg said that while he had not been interviewed by Mueller’s team, others have. He did not want to disclose further details.

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“I want to be careful here because that, our work with the special counsel is confidential, and I want to make sure that in an open session, I’m not revealing something that’s confidential,” Zuckerberg told Leahy.

Zuckerberg clarified that he did not know anything about the special counsel serving a subpoena to anyone at Facebook.

“I actually am not aware of a subpoena,” Zuckerberg said. “I believe that there may be, but I know we’re working with them.”

During the Senate hearing, the Facebook mogul also acknowledged the company’s and his own part in failing to stop the Cambridge Analytica breach. The political firm Cambridge Analytica was hired by President Donald Trump’s campaign and was able to access information from over 50 million Facebook users. Zuckerberg said the firm bought the information from an application developer.

Now, Zuckerberg said, Facebook will address the scandal by getting to the bottom of what exactly Cambridge Analytica did.

“It’s not enough to just connect people,” Zuckerberg said. “We need to make sure those connections are positive.”

Facebook will now ban any app developer that misuses its information, and it will ensure that developers cannot access as much information as they used to in order to prevent another breach of data.

The company will also look into Russian influence on elections via Facebook. Zuckerberg said it is deploying new artificial intelligence tools to better track fake accounts.

“This is an arms race,” Zuckerberg said. “They’re gonna keep getting better at this.”