PATH service was suspended between Hoboken and Journal Square after the incident, which apparently took place around 5:30 a.m.
According to media reports, two people bumped into each other inside the train. One person reportedly started shooting, and the commotion spilled onto the platform. Apparently, another person may have also fired a gun.
The number and condition of victims was unknown, with some reports saying as many as three people may have been wounded.
The closure came at an inopportune time for fans heading to the final day of the Barclays golf tournament in Jersey City. However, the light rail train was cross honoring tickets.
The last two months in Jersey City have been unusually violent, with a spate of shootings and gun deaths that so far has defied explanation. Eight murders have occurred since the end of June. Until this summer, the murder rate had been declining in the city.