"Effective immediately, we are temporarily closing our office buildings and all badge access will be suspended. Offices will reopen on Monday, November 21st," reads the letter to Twitter staff as seen by the BBC.
"Thank you for your flexibility. Please continue to comply with company policy by refraining from discussing confidential company information on social media, with the press or elsewhere. We look forward to working with you on Twitter's exciting future."
Musk has described Twitter as "a software and servers company" at its core, which is why he thinks engineers who code should take priority over other resources.
He has tweeted several ambiguous statements about Twitter in the past few hours, including a post with skull and crossbones emoji, an image of Twitter's blue bird icon on a gravestone and on the face of a man posing next to it with two fingers pointed in the V for 'victory' sign. Another tweet from Musk claims that "we just hit another all-time high in Twitter usage lol".
"Let that sink in …", he wrote, appearing to refer to the video of him carrying a sink into Twitter's headquarters on the day he took over the company.
He also made a joke about his $44 billion purchase of the social media company.
"How do you make a small fortune in social media? Start out with a large one."