TORONTO - Thomson Reuters Corp Chief Executive Jim Smith was taken to a Toronto hospital on Monday "after feeling unwell" and remains under observation at the hospital, the company said on Tuesday.

In his immediate absence, Chief Financial Officer Stephane Bello will oversee Smith's responsibilities alongside his own, Thomson Reuters said in a statement.

Two weeks ago, Smith struck a deal to sell a majority stake in the company's Financial and Risk business to U.S. private equity firm Blackstone Group LP. The deal, which valued the unit at around US$20 billion including debt, is expected to close in the second half of 2018, Thomson Reuters has said.

A former journalist, Smith was appointed CEO in January 2012. He began his career at Thomson Corp in 1987 and ran its North American newspaper business before moving into other executive roles, including managing the professional publishing business that served the legal, tax and accounting markets.

Last year, Smith and other members of Thomson Reuters' executive leadership moved to Toronto from Stamford, Connecticut.

The Blackstone deal that Smith oversaw is the company's biggest transaction since Canada's Thomson Corp bought London-based Reuters Group Plc in 2008. The Financial & Risk business accounts for more than half of Thomson Reuters revenue and supplies news, data and analytics to banks and investment houses around the world.

Canada's Thomson family owns 64 per cent of Thomson Reuters through its Woodbridge investment vehicle.

Bello joined Thomson in 2001 and was formerly CFO of the professional division. He holds law and economic degrees, and previously worked at General Motors Co.