“Anyone who wishes to do remote work must be in the office for a minimum (and I mean minimum) of 40 hours per week or depart Tesla,” the memo said.

Reuters could not immediately verify the authenticity of the memo. Tesla did not respond to a request for comment. Musk could not be reached for comment.

In response to the memo that was tweeted from an unverified account, the billionaire, who has proposed to take Twitter Inc private in a $44 billion deal, said, “They should pretend to work somewhere else.”

Musk would “review and approve” any cases where they could not meet the minimum, according to the memo.