Somerville began reopening a stretch of bustling Davis Square Tuesday night as workers rushed to shore up a historic building that the city believed was at risk of collapse.
One lane of Elm Street opened to traffic just before 9 p.m., said Jackie Rossetti, a spokeswoman for the city.
The lane in front of the Social Security building at 240 Elm St., which was deemed unsafe, remained closed, along with Chester Street.
“The general message to the public is that the square is open, but vehicular traffic is problematic,” said Stephen Mackey, president and chief executive of the Somerville Chamber of Commerce.
Elm Street between Dover and Grove streets was shuttered on Monday amid fears over the aging structure. Mayor Joseph Curtatone said a company hired by the building owner alerted officials to the concern, which he worried could be a threat to public safety.
“How the building was designed and how the roof is attached to the walls, there is the potential for significant collapse,” Curtatone said by phone.
By Tuesday afternoon, officials determined that the area across the street from the building was out of harm’s way, and said they would soon reopen half of Elm Street.
The area directly in front of the Social Security building, and two businesses nearby, could remain closed until next week. A total of 17 businesses were initially affected.
The city has previously raised concerns about the safety of the building. In 2013, a part of the building fell to the sidewalk. The building’s owner put up scaffolding to protect pedestrians soon after, but city officials claim the owner never completed required repairs.
In April the city finally lodged an application for a criminal complaint against the owner, listed on the filing as Michael A. Argiros, Charles River Realty Group LLC, for failing to comply. A hearing on that matter is set for August.
According to public records, Alexander A. Argiros trustees and Davis Square Realty Ventures purchased the building for $7.8 million in 2011.
Neither Michael or Alexander Argiros could be reached for comment.
City officials announced last August that Roche Bros. had plans to open a Brothers Marketplace in the first floor of the building. But Curtatone said the company recently pulled its proposal.
A spokeswoman for Roche Bros. confirmed that the project fell through in May. She declined to explain why.
Globe correspondent Jacqueline Tempera contributed to this report. Steve Annear can be reached at firstname.lastname@example.org. Follow him on Twitter @steveannear. Catherine Cloutier can be reached at email@example.com.