New Jersey Transit police were called around 12 a.m. for an incident on a light rail train between Norfolk Street Station and Orange Street Station.
Police arrested a male suspect who remained on board the light rail, which had been brought into Orange Street Station.
Three adults and the suspect were transported to a local hospital with non-life-threatening injuries.
Newark Light Rail remains in service but is bypassing Orange Street Station.
New Jersey Transit Police are leading the investigation.
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