Police announced the arrests on Tuesday morning after executing search warrants on Monday.
A search warrant was issued at a home in Amityville in Babylon, New York, and at least two people inside the house were arrested after police spent the entire night at the residence.
No remains were found there, police said.
It was also revealed Tuesday that state police assisted Suffolk County police at Bethpage State Park, where they found more remains.
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The Suffolk County medical examiner previously said a female head, right upper leg, left leg from the knee down and right arm and two male arms were found. Autopsies are underway to determine the identities of the victims and what happened to them.
It is believed that the female body parts are that of a 59-year-old woman.
The grisly discoveries began Thursday morning, when a group of teenagers walking near Babylon Memorial Grade School found a severed arm on the side of the road at the edge of Southard Pond Park.
When officers arrived and searched the area, they found a second arm about 20 feet from where the first arm was found. Police say both appear to belong to a 53-year-old man.
As the search expanded Thursday afternoon and into the night, a cadaver dog found a woman's leg, arm and head on the opposite side of the park, near Babylon Elementary School.
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At a Friday morning press conference, detectives said the condition of the remains suggests they had not been in the park long - maybe a few days or even hours.
Police said the incident appears to be isolated, and there is no threat to the public.