Power is out from Union Beach facing Staten Island south to Wall, just north of Ocean County, Office of Emergency Management officials said.
A code red reverse 911 call has been made to all county residents, asking them to stay home "until the traffic situation can be figured out,” Sheriff Kim Guadagno said.
Customers have also lost service in several Ocean County towns including Lakewood, Toms River and Barnegat, according to the website for Jersey Central Power & Light.
So far the outage has affected thousands of customers and shut down traffic lights on major roads including Route 36, just in time for rush hour.
Guadagno said all available officers are working traffic control, and, as of 6:30 p.m. Tuesday, "doing a good job."
An OEM official said they know JCP&L has a transformer issue, and that there are unsubstantiated reports that a major transformer may have exploded.
"Calls are coming in like crazy," said Peter Johner, a spokesman for the utility company.
Lights started flickering shortly before 6 p.m. Tuesday. Power began to come back on at about 7 p.m.
Johner said JCP&L is currently trying to determine the cause of the problem, but said the scope of the outage suggests the problem is with the transmission and not distribution.
Further details about the extent of the outage were not immediately available.
Hazlet police encouraged drivers who would normally take Route 36 to use local roads, and said additional officers have been dispatched to monitor traffic.
The population of Monmouth, New Jersey's northernmost shore county, is just over 600,000.
