Officials have increased security Tuesday following Monday's Boston Marathon explosions.
NJ Transit spokesman John Durso Jr. says passengers are monitoring their surroundings and, in some cases, have alerted officials about their concerns.
State Police Lt. Stephen Jones says there is no known threat. But the agency's bomb unit, aviation crews, tactical teams, and search and rescue assets have been deployed as a precaution.
The Port Authority also is on a heightened state of alert at bridges, tunnels and on its PATH rail line between New Jersey and New York.
Atlantic City's 12 casinos remain open, and executives say they have not been told by authorities to undertake any unusual security measures.
New Jersey Transit released the following statement on Monday:
"As a result of today's tragic events, NJ TRANSIT is currently in a heightened state of alert. While there has been no specific threat made to our transit system at this time, NJ TRANSIT police have deployed both uniformed and plain clothed officers to further patrol our system and keep our customers safe. NJ TRANSIT police are also in constant communication with local, state and federal authorities. We are reminding our customers to observe their surroundings and report any suspicious or unusual activity to NJ TRANSIT police. Again, that number is 1-888-TIPS-NJT. The hearts and thoughts of all of us at NJ TRANSIT go out to those affected by this senseless tragedy."