The incident happened near Packard's Corner in Allston on around 1:40 p.m. on Monday afternoon, June 12, the MBTA reports.
Buses replaced service between Kenmore and Washington Street while personnel worked to re-rail the trolley car.
The cause of the derailment is under investigation. The Federal Transit Administration (FTA) and the Department of Public Utilities (DPU) have both been notified.
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