Emergency services were scrambled to the sprawling property in Colts Neck shortly before 6pm GMT (1pm local time).
Some US media reports say up to five bodies have been discovered though it is unclear whether they were shot or killed by the blaze which ripped through the mansion.
Monmouth County Prosecutor’s Office spokesman Chris Swendeman said: “Our office is on the scene of a fire in Colts Neck with multiple fatalities.
“Firefighters are still working on the fire so the investigation is ongoing.”
Police are scheduled to hold a press conference imminently to provide an update on the incident.
This is a breaking story. More to follow…