The MBTA says the Green Line is being replaced by shuttle buses between Government Center and Lechmere and the Orange Line is suspended between North Station and Back Bay due to a "structural issue" with the Government Center garage on Thursday afternoon.
The MBTA says service is expected to be impacted for several days, and that it will not resume until emergency repairs are conducted and it is deemed safe.
Commuters are urged to use Green Line service through downtown.
It's been almost exactly three months since a worker was killed after the partial collapse of a crane and parking garage under construction at Government Center.
Crane operator Peter Monsini, 51, of Easton, was killed when his crane came down approximately nine stories with a large amount of debris on March 26. The project is located right over a series of Massachusetts Bay Transportation Authority Orange Line tunnels.
In the immediate aftermath of the collapse, roads were closed and Orange and Green Line service was replaced by shuttle buses while investigators determined the safety of the structure.
When Orange Line service resumed several days later, those shuttle buses were discontinued and riders were pointed to the Orange Line. Green Line service between North Station and Government Center didn't resume until April 9.
The MBTA said Thursday evening that HYM Construction, the contractor tasked with demolishing the garage, told the agency support columns in tunnels near Haymarket are "severely deteriorated," leaving them unsafe for trains to travel through.
MBTA General Manager Steve Poftak blamed the contractor directly.
"This service disruption as a result of HYM's project is unacceptable and the MBTA will seek to hold HYM Construction accountable for all costs associated with this event," Poftak said in a statement Thursday night. "Riders' safety is our top priority and unfortunately, as a result of this private party's project, we must divert trains until the tunnels can be inspected and cleared by independent experts."
But HYM said the issue is "unrelated" to its work.
"This afternoon a team of engineers conducted a survey of the MBTA tunnels underneath the Government Center Garage. A subsurface column in proximity to the Green and Orange Lines was identified as compromised from years of water damage," read a statement Thursday night from the National Real Estate Advisors and the HYM Investment Group. "The condition of this column is unrelated to the demolition work at the Government Center Garage. In an abundance of caution, the MBTA is diverting operations around the Haymarket MBTA Station."
MBTA officials said more than 100 tons of debris were removed from directly above the Green Line and structural engineers carefully assessed the tunnels to ensure their safety. Engineers were expected to continue to monitor the tunnel.
The demolition is all part of the $1.5 billion Bullfinch Redevelopment Project. The finished project is expected to include a parking garage surrounded by office and apartment buildings. The site has been under demolition for some time.
The Occupational Safety and Health Administration, the Suffolk District Attorney and Boston police are still investigating the collapse.
The latest Government Center woes are just the latest in a series of issues that have plagued the MBTA in recent months.
Just last week, Federal Transit Administration demanded immediate changes to address glaring safety issues in a report released. Those issues included a pattern of crashes, derailments, speeding and signal issues.
The federal agency began investigating the MBTA in April after a recent death and several incidents that caused injuries. The directives issued by the FTA require the MBTA and the state Department of Public Utilities to collaborate on fixing the issues and improve the culture of safety at the MBTA.
The MBTA said it has been fully engaged with the FTA during its inspection and work is underway to address the issues that were flagged.
Massachusetts lawmakers announced last week that they are planning to hold hearings in July to discuss the report and learn more about the T's operations and management. The MBTA's board of directors also met Thursday to discuss the findings.