Twitter announced Thursday, Nov. 17, it would close all of its offices until at least Monday, Nov. 21, following an ultimatum from the San Francisco-based social media company's new owner, Elon Musk.

Musk sent a companywide email last week telling employees to expect "long hours at high intensity" if they wished to retain their jobs — reportedly prompting a rash of resignations.

Since the billionaire Musk assumed control of Twitter in late October, a combination of layoffs and voluntary employee departures have rocked the microblogging and social networking service founded in 2006.

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