Twitter is facing the exit of key managers, even as the company struggles with flagging growth in its user base.CEO Jack Dorsey is trying to counter the company’s flagging growth in user base

CEO Jack Dorsey said in a tweet late Sunday that senior vice president of engineering Alex Roetter, vice president of global media Katie Jacobs Stanton, senior vice president of product Kevin Weil, and Brian Schipper, vice president of human resources were quitting the company.

“All four will be taking some well-deserved time off. I’m personally grateful to each of them for everything they’ve contributed to Twitter and our purpose in the world,” wrote Dorsey in the message.

Jason Toff, general manager of video-sharing app Vine, also announced in a Twitter message that he was leaving Vine to join Google to work on virtual reality.

Dorsey said Roetter and Weil had during their over five years tenure with the company scaled the ads product and engineering teams from generating near-zero revenue to an over-US$2 billion run rate it has now, while Stanton helped expand content operations and started international offices such as in Japan, the U.K. and Ireland. Schipper had scaled recruiting and HR functions globally, Dorsey said.

Earlier news outlets reported that in a shakeout in top positions at the company, Roetter, Stanton, Weil and Toff were leaving the company. At least one of them was asked to leave, according to The New York Times.

A Twitter spokeswoman said the company had nothing to add beyond Dorsey’s message, which was in response to what he described as “inaccurate press rumors.”

COO Adam Bain will be taking over temporarily additional responsibilities  including for revenue-related product teams, the media group and the HR team, Dorsey said. CTO Adam Messinger will take charge of “all of engineering and consumer product, design and research, user services, and Fabric into one group,” he said. “And I will be partnering with him day and night to make sure we are building the right experiences.”