Boston-based Essex River Ventures, which specializes in acquiring and selling underperforming properties, has been purchased by one of Canada’s largest commercial real estate services companies for an undisclosed sum.

Avison Young, which bills itself as "Canada’s largest independently-owned commercial real estate services company," purchased Essex River and plans to maintain its Boston office, according to a statement. It is the firm’s sixth location outside of Canada.

Essex River was founded in 2003 by CEO John Fenton. Effective immediately, Fenton will become a principal of Avison Young and managing director of the company’s Boston office.

"We will continue to expand in the Boston area, both in the suburban markets as well as downtown, and will look to add complementary leadership to John as well as fill in the service platform across the four property types (office, retail, multi-family and industrial) and multiple service lines that our clients require," Earl Webb, Avison Young’s president of U.S. operations, said in a statement.

The following Essex River executives will also join Avison Young: K. Beth O’Donnell, director, client services; Tom Palmer, senior property manager; Brian Hodess, director, construction services; and Kathy Shepherd, administrative manager.

Avison Young opened its first U.S. office in Chicago in 2009, followed by U.S. offices in Washington, D.C.; Atlanta; Houston; and Tysons Corner, Va., over the past year. The company also acquired Atlanta-based Hodges Management and Leasing Co. and Tysons Corner, Va.-based Appian Realty Advisors LLC in July.