More than 20 tech and civil society leaders, including the chief executives of five of the 10 biggest U.S. companies, appeared at a closed-door Senate meeting on Wednesday to shape how artificial intelligence is regulated.

The meeting, which was organized by Senate Majority Leader Chuck Schumer, included a prestigious, and possibly combustible, mix of personalities with diverging views on how to write the rules for AI. The CEOs of Alphabet, Microsoft, Meta Platforms and OpenAI were invited to appear alongside rivals and industry critics to discuss possible guardrails for AI that balance the risks and rewards of the technology.

Areas of disagreement were apparent throughout the morning session, according to several people who were in the room. Meta CEO Mark Zuckerberg, OpenAI CEO Sam Altman and Microsoft co-founder Bill Gates offered diverging views on the risks of open-source AI research, according to people in the room. Tesla CEO Elon Musk was also met with pushback from Berkeley researcher Deb Raji for appearing to downplay concerns about AI-powered self-driving cars, according to one of the people in the room.