NEW YORK (CNNMoney)

Musk, who promises to take humans to new heights with space and battery technologies, was especially grounded in his latest caution on artificial intelligence.

He told an audience at MIT on Friday that "we should be very careful about artificial intelligence," warning it may be "our biggest existential threat."

"With artificial intelligence, we are summoning the demon," he said.

"In all those stories where there's the guy with the pentagram and the holy water, it's like yeah he's sure he can control the demon," he continued, to some laughs from the audience.

Musk then cracked a smile: "Didn't work out."

His Tesla (TSLA) electric vehicles and SpaceX rockets, which recently won a multi-billion dollar contract with NASA, have pushed the limits of their respective technologies.

Musk hasn't embraced artificial intelligence, a field of study at MIT and other schools with significant ethical considerations and business potential. He has previously cautioned it is "potentially more dangerous than nukes."

But he has invested in artificial intelligence companies -- because, he told CNN's Rachel Crane recently, he wanted "to keep an eye on them."

"I wanted to see how artificial intelligence was developing," Musk said in the CNN interview. Among his questions: "Are companies taking the right safety precautions?"

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Elon Musk warns against unleashing artificial intelligence 'demon'