A door came off a moving MAX train and made contact with equipment near the Sunset Transit Center on Thursday.
A TriMet spokeswoman said the door on the left side of the eastbound train had a mechanical issue earlier in the day. The exact issue was not immediately known.
The door was not in service when it came off at around 11:30 a.m. The door hit a metal box on the wall of the tunnel, according to a TriMet spokeswoman.
TriMet is investigating why the door was not effectively secured and how it was able to detach from the train.
There were 40 people on the train at the time. Nobody was hurt and everyone was safely evacuated.
MAX service was restored in the area at around 1:15 p.m.
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