SPRINGFIELD — Colliers Capital Markets announced that it has been retained by MassDevelopment, to sell 1550 Main Street, the 128,900 square-foot office building in Springfield’s downtown corridor.

Colliers Executive Vice President Jeanne Pinado will lead marketing efforts of 1550 Main, with Vice President Rob Schlesinger providing additional support, and the firm will issue a call for offers in mid-July.

The five-story office building is 97% leased and underwent a complete $9 million renovation in 2010. Capital improvements included creating a high-quality building entrance with an open atrium with 70-foot ceilings, as well as building an outdoor plaza and improving landscaping, elevators, restrooms and more.

Formerly a federal courthouse, 1550 Main St. is home to tenants such as the administrative offices for Springfield Public Schools, the United States General Services Administration, and BayState Health. The building has a 103-space below grade garage and connects via a pedestrian skywalk to the 28-story Tower Square, an office, retail, hotel and parking complex. MassDevelopment purchased 1550 Main from the federal government in 2009 and revitalized the campus to position it as a Class A office building with an expansive public plaza as part of an economic development initiative.