Some Orange Line riders face three weeks on shuttle buses following derailment

MBTA officials were inspecting the derailed Orange Line train outside Wellington Station.Matthew J Lee/Globe staff

Some Orange Line riders instead traveled Wednesday on shuttle buses, a change in routine they will face for the next three weeks while the MBTA repairs derailment damage and assesses, once again, the safety of its new generation of subway cars.

A six-car train carrying 100 passengers derailed Tuesday as it was moving through a work zone at Wellington Station in Medford. The MBTA is working to repair the damage as well as complete the upgrade that was already underway at the site, said Joe Pesaturo, spokesman for the Massachusetts Bay Transportation Authority.

No injuries were reported.

The shuttles are in place from Oak Grove Station in Malden to Sullivan Square in Charlestown. The other affected stations are Malden Center, Assembly, and Wellington.

To help facilitate our ongoing Orange Line infrastructure upgrades at Wellington and address damage from the derailment, shuttle buses will continue to replace service between Oak Grove and Sullivan Square for the next 3 weeks.

— MBTA (@MBTA) March 17, 2021

The T also said it was pulling its next-generation Orange Line cars and a six-car Red Line train out of service to conduct safety inspections in light of the derailment. It is at least the third time the cars will be offline since they were put into service in August 2019.

The first new six-car trains, manufactured in Springfield by the Chinese company CRRC, were introduced months later than expected and taken out of service in September 2019 and again in March 2020. In both instances, inspectors found a problem with bolsters in the underbody of the trains where the chassis meets the carriage.

The new Orange and Red Line cars will undergo an analysis of their performance, according to the T.

The derailment, at 11:40 a.m. Tuesday, occurred when a northbound train moving at a slow speed was crossing over to the southbound track to accommodate ongoing maintenance work, Pesaturo said.

The cause remains under investigation.