Twitter CEO Elon Musk said on Thursday that he's hired a new chief executive for the social network and that he will take on a new role overseeing products, software and system operations.

Musk didn't name his replacement but indicated in a tweet that the person is a woman.

Musk said in December that he planned to step aside as CEO of Twitter once he found a replacement to take the helm at the San Francisco-based social network. The tech mogul, who also runs Tesla and Space X, has merged Twitter with a new entity called X Corp.

Musk's announcement on Thursday set off a wave of speculation about who the new CEO of the troubled social network may be.

The Wall Street Journal reported that Linda Yaccarino, NBCUniversal’s head of advertising, is in talks to take the role. Yaccarino has spent more than a decade at the media giant, helping to launch NBCUniversal's ad-supported streaming TV service, Peacock.

Twitter didn't comment on the reports.

Musk's tenure as Twitter CEO has been marked by drastic cost-cutting and other controversial moves, such as reinstating accounts that had previously been banned. Advertisers have reportedly paused spending on the platform over concerns about racist, sexist or other problematic content that could jeopardize their brands.

Musk reportedly pegged Twitter's value in a March email to staff at $20 billion, less than half of the $44 billion he paid for the firm in a transaction that closed last October.

In April, the San Francisco Board of Supervisors passed a resolution urging city departments not to sign up for Twitter Blue, a paid subscription service that offers "blue check" verification and other features.