An executive and two former employees of WPP, one of the world’s biggest advertising companies, have been arrested in China, according to two people familiar with the situation.

The arrests involved WPP’s GroupM media trading division and included a raid on offices in Shanghai, said the people, who asked not to be identified because they weren’t authorized to speak publicly.

WPP declined to comment. The Chinese Embassy in London didn’t respond to a request for comment. The Financial Times reported on the matter earlier Friday.

Greater China, a WPP division that includes Taiwan, made up 5% of the company’s revenue in 2022, according to the firm’s annual report.

The region ranked as the company’s No. 4 territory behind the U.S., U.K. and Germany in 2022 and is the world’s second-largest advertising market, according to WPP’s annual report.

However, ad spending overall is estimated to have fallen 0.6% last year in China due to COVID-related lockdowns, WPP said.

At the beginning of 2023, the London-based company opened its third campus in the country, in Guangzhou.

Beijing has been intensifying its scrutiny of Western businesses amid growing tensions. In April, Bain & Co. confirmed that Chinese authorities had questioned staff at its Shanghai office.

The following month, Chinese state security officials visited a branch of Capvision, a consulting firm with headquarters in New York and Shanghai.