NEW YORK (Reuters) – ByteDance, parent company of the short video app TikTok, has more than tripled its U.S. employees in the past 12 months, the company said in response to a Reuters inquiry.

ByteDance said it now has over 1,000 employees across the country from Mountain View, California to New York, up from around 300 this time last year.

Main increases came from engineers handling research and development, data security, creator teams and sales teams, ByteDance told Reuters.

TikTok’s Chinese ownership and wide popularity among American teens have brought scrutiny from U.S. regulators and lawmakers. Regulators questioned the safety of the personal data the app handles and if its Chinese ownership poses a national security risk, Reuters first reported last year.

TikTok has been hiring more U.S. engineers to reduce its reliance on staff in China, and has set up a team in Mountain View, California to oversee data management, sources familiar with the matter have said.

Most recently the China tech giant has been shifting its center of power away from China, hiring senior executives and expanding its presence in the United States, Reuters reported last month.

ByteDance recently hired Walt Disney Co’s Kevin Mayer as its COO, and CEO of TikTok. It also hired veteran data security executive Roland Cloutier. The company will hire an additional 100 security, data, and privacy protection people by the end of this year, Cloutier said in a blog post this week.

ByteDance said it had approximately 60,000 employees worldwide as of January, mostly based in China. The company bought out social media app Musical.ly in 2017, when it employed around 20 people in the U.S. at that time, sources said earlier. Musical.ly laid the foundations for TikTok’s rapid growth.