An Orange Line train derailed in a work zone at Wellington Station in Medford Tuesday morning, prompting the MBTA to pull the system’s newest subway cars from service and to plan for three weeks of shuttle bus service, officials said.
The derailment, of one of the brand-new Orange Line trains being phased into service, happened at 11:40 a.m., said Joe Pesaturo, spokesman for the Massachusetts Bay Transportation Authority.
On Tuesday night, Pesaturo said that while the cause of the derailment had not been determined, the MBTA’s four new six-car Orange Line trains and one new Red Line train were temporarily taken out of service “to allow vehicle engineers to perform a thorough analysis of the cars’ performance.”
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No one was injured in the derailment, which occurred when a northbound train moving slowly was crossing over to the southbound track to accommodate maintenance work, Pesaturo said. About 100 passengers were on board.
The Medford Fire Department’s deputy chief, John Freedman, said the train derailed “in the middle” and noted the train’s front and rear cars remained on the track.
Firefighters cleared the scene just before 1 p.m., Freedman said.
Pesaturo confirmed that the derailed train was part of the fleet of new Orange Line trains being put into service. They are manufactured in Springfield by the Chinese company CRRC. The train was comprised of six cars that entered service on varying dates, Pesaturo said.
Two of the new trains had to be temporarily removed from service in 2019 for repairs.
Tuesday morning’s derailment stopped train service between the Community College and Oak Grove stations, with shuttle buses replacing trains, according to tweets from the MBTA. The bus shuttle route was later shortened to remove Community College, Pesaturo said.
Shuttle bus service is expected to continue between the Oak Grove and Sullivan Square stations for three weeks while workers replace a decades-old track switch that was damaged during the derailment, Pesaturo said in a separate statement Tuesday evening.
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The MBTA will also make additional infrastructure upgrades and improvements at stations along the Orange Line, he said.
Five stations were affected by the derailment: Sullivan Square, Assembly, Wellington, Malden Center, and Oak Grove. Officials told riders to expect delays.
An investigation into the cause of the derailment was underway, Pesaturo said.
Crews were working to get the train back on the track and to inspect track and signal infrastructure in the area, an MBTA tweet said.
John R. Ellement of the Globe staff and correspondent Andrew Stanton contributed to this report. Charlie McKenna can be reached at charlie.mckenna@globe.com. Follow him on Twitter @charliemckenna9.