Mass Innovation Labs announced a Boston expansion for the second time this week at Thursday’s Related Beal groundbreaking in the Seaport.

The developer moved forward on the first phase of its 375K SF Innovation Square, or iSQ, in the Raymond L. Flynn Marine Park Thursday. The $73M endeavor at 6 Tide St. will be anchored by Mass Innovation Labs, a biotech accelerator that announced Monday it was also expanding to Boston Landing.

“Mass Innovation Labs is the perfect tenant to kickoff iSQ,” Related Beal Executive Vice President Stephen Faber said in a prepared statement. “They nurture innovative, entrepreneurial, high-growth organizations with the potential to create a substantial economic engine for Boston and the Commonwealth. We believe the Ray Flynn Marine Park in the Eastern Seaport has all of the ingredients to be the next great life science cluster.”

The first phase of Innovation Square includes a four-story, 125K SF R&D, building and is expected to completed in Q1 2019. Related Beal and partner Kavanagh Advisory Group executed the Mass Innovation Labs lease for 54K SF on the building’s first two floors.

The groundbreaking was attended by Boston Mayor Martin Walsh, who jokingly lamented the loss of the city’s biggest snow farm. The Related Beal property was used to store plowed snow and garnered attention after the record-setting 2015 winter when it took until July of that year for a 75-foot snow pile to fully melt.