"The challenges obviously that it is burning so it is hard to go in there and try to recover remains when there is potential risk of the roof falling in or things like that", Monmouth County Prosecutor Chris Gramiccioni said.
He says one body was found out front.
Gramiccioni said officials are investigating whether the fires are connected.
Both fires appear to be suspicious, according to authorities.
More than 20 fire departments responded to the blaze, which was reported on Willow Brook Road in tony Colts Neck at 12:38 p.m., officials said.
It remains unknown if Caneiro's gunshot wound was self-inflicted, but Monmouth County Prosecutor Christopher Gramiccioni said there was not threat to the public. But he insisted, "We have no reason to believe that anyone in the community is in any danger at this time".
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About 3,000 people from the first of the caravans have arrived in Tijuana, Mexico, across the border from San Diego, California. USA and California state flags fly behind the border wall, seen from Tijuana, Mexico, Monday, Nov. 19, 2018.
Investigators said they found several gas cans behind the home.
Dramatic news helicopter photographs showed flames billowing from the modern mansion, which has a large garage and swimming pool, and is located around 50 miles south east of Manhattan.
The 5,700-square-foot home has four bedrooms and five bathrooms, according to Zillow. It's home to horse farms and some homes in the town of 10,000 are valued at around $750,000 each, AP noted.
The victims have been named by U.S. media as Keith Caneiro, 50, his wife Jennifer Caneiro, 45, and their two young children.
Caneiro's LinkedIn profile describes him as the CEO and chief technology officer for a company in the New York City area called Square One. His profile says he graduated from Columbia University with a Master of Science degree in 2018 and previously received certifications from Harvard Business School.
It is now unclear whether those victims were also shot dead, or died in the subsequent blaze, NBC10 reported. Paul Caneiro is identified online as the vice president of Square One. "Any little bit can constitute a piece of the puzzle that can make things clearer". "The other three were recovered from the inside of the home", Gramiccioni said.