WESTBROOK — Maine Medical Center has purchased One Riverfront Plaza for $10.75 million, a sale that will bring 400 to 500 workers to the downtown, according to an MMC spokeswoman.

The office building, vacant since November 2015, will house the medical center’s integrated Information Services employees along with other administrative functions currently spread across eight office locations throughout Greater Portland, according to Thursday’s announcement.

MMC expects to have all the employees in place in Westbrook by the end of the year.

“Westbrook is excited to welcome Maine Medical Center, Maine’s premier medical organization, into an expanded role in our city as we continue our growth. Their purchase and use of this location on the river will be key to the ongoing development of our downtown.  We have appreciated their presence in our community over the years and look forward to partnering with them in more significant ways with this major investment,” Mayor Michael Sanphy said in a statement.

The 134,000-square-foot building was purchased from One Riverfront Plaza Holdings, LLC. It was last occupied by insurer Disability RMS, which moved to South Portland in November 2015. Disability RMS had occupied a large portion of the building, built in 2004. The move was an economic blow to the city.

The city has valued the building, on 0.85 acres, with some Presumpscot River frontage, at $20.55 million, according to city tax records. Those records also show Pendleton Westbrook bought One Riverfront Plaza for $23.5 million in 2005.

Earlier this year the building went to auction after the bank filed a foreclosure notice. The building was bought back at auction Feb. 17 by The U.S. National Bank Association for $9.2 million.

The bank then accepted private bids for the purchase of the building, which were expected to be opened at the end of April.

“We are incredibly excited to bring our Information Services team together in one location. We believe this will increase our team’s operating efficiencies and ultimately benefit our providers, nurses and the patients who benefit from their care,” said Marcy Dunn, senior vice president and chief information officer for Maine Medical Center and MaineHealth.

Kate Gardner can be reached at 781-3661 ext. 125 or [email protected]. Follow her on Twitter: @katevgardner.

Maine Medical Center is the new owner of One Riverfront Plaza.