A pro-ISIS Twitter account published a list of New Jersey Transit officers' names and personal information, encouraging supporters to carry out "lone wolf" attacks on them, according to sources and published reports.
The group known as the Caliphate Cyber Army (CCA) first released the personal details of 55 officers in early March after hacking into the NJ Transit police website, Newsweek reported. The newsmagazine saw the list of personal details, which included home addresses, phone numbers, names and ranks.
The Twitter account that linked out to the list has since been suspended, but another tweet referencing the list was sent Monday, sources told NBC 4 New York. It's not clear who sent the tweet.
The original file was uploaded to an Arabic-language file sharing site on March 2 and was downloaded 300 times by March 5, the Daily Mail reports.
In a statement, NJ Transit spokeswoman Lisa Torbic said the agency's information system was not compromised, "however some information was breached from an outside vendor."
"The New Jersey Transit Police Department is working with the Department of Homeland Security and the FBI on this matter," she added.
The FBI said it was aware of the situation and providing assistance to the New Jersey Transit Police Department.
Sources told NBC 4 New York they do not believe there is any credible threat.
The hacking attacks have been described as unsophisticated, and experts monitoring the CCA site told Newsweek they show the group has limited technical skill sets.
But, as the quoted expert pointed out, "their activities shine a light on just how vulnerable websites are out there."
Jonathan Dienst contributed to this report.