WBUR's Walter Wuthmann said he saw sparks coming from the B Line train while it pulled into Park Street just before 3 p.m.
Videos posted to social media showed people running from the train and Boston Fire responding to the scene.
The incident caused travel delays of up to 20 minutes and shuttle buses were eventually brought in to replace service from Kenmore to Government Center as a result. The MBTA later labelled the issue as a "wire problem."
No other information was initially released.
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