Multi-Employer Property Trust (MEPT) has added to its portfolio of Boston assets with the $33.25 million acquisition of 147 Milk St., a 52,337-square-foot office building occupied by Atrius Health.

Colliers International’s Doug Jacoby, Scott Dragos, Tony Hayes, Tim Mulhall and Dan Hines represented seller, Lexington Realty Trust. Lexington acquired the 96-year-old building in March 2007 for $20 million, according to data from The Warren Group, publisher of Banker & Tradesman.

Backed by public pension plans, the $7.6 billion MEPT fund has been aggressively snapping up Boston real estate in the past two years, acquiring land and buildings in Fort Point and the South End.

It’s partnering with Leggat McCall Properties on a 710-unit apartment proposal off Harrison and Albany streets in the South End, after acquiring a group of parcels there and in Fort Point for $250 million.

In October, MEPT paid $162.5 million for four parcels in Fort Point including the Stillings Street parking garage and office buildings on Farnworth and Sleeper streets. It also bought the Necco Street parking garage in January 2015 for $56 million.