A routine visit by child welfare authorities on Long Island led to a multicounty search for a boy who was mysteriously absent, an Amber Alert for one of the boy’s half-brothers and the discovery of a small body in a shallow grave in the backyard of the family’s home, the police said Saturday.
The chain of events began Wednesday, Major Patrick Regan of the New York State Police said. Representatives of Suffolk County Child Protective Services visited the home of Robert Rodriguez and Heather Kowalczik in Farmingdale to check on their 6-year-old son, Alex, who is autistic.
At some point, Major Regan said, Ms. Kowalczik mentioned that she had three children, Alex; Robbie, 9; and Justin, 3. However, Major Regan said, the child welfare agents could account for only two boys, Alex and Robbie.
Ms. Kowalczik told the investigators that Justin was with relatives in Orange County, where the family used to live, Major Regan said. The Suffolk child welfare authorities then contacted their counterparts in Middletown, N.Y. An agent in Middletown called the State Police there, who contacted troopers on Long Island, Major Regan said.
When the State Police spoke with Ms. Kowalczik, she made statements that prompted them to begin digging in the backyard of the two-story cream-color house on Hallock Road.
Then on Friday, the police became alarmed when Robbie did not show up for school. They issued an Amber Alert and eventually found the child with his father, Mr. Rodriguez.
After digging near a corrugated metal fence at the edge of the yard, the authorities found the remains, buried in a grave no more than 3 feet deep. The police said they believed that the body had been there since July 2010.
The police also said they believed that the body was Justin’s, and were investigating the case as a homicide. The medical examiner’s office was to determine the cause of death.
On Saturday neighbors gathered near the house, where a statue of the Virgin Mary stood in the front yard, which was cordoned off by yellow police tape.
One of the neighbors, Michele Peavey, 49, said that Ms. Kowalczik came to her house crying on Friday morning. Ms. Peavey’s husband, Jimmy, 53, said that Ms. Kowalczik seemed unusually burdened and that he thought that she was on the verge of confiding something, but then left.
“She said, ‘See you later,’ but she never came back to our house,” he said.
Ms. Peavey said that Alex had been in a hospital for a few weeks. The Peaveys said they had never seen a third child.
“There was never a baby here,” Louie Lancia, who owns the house, said. “All of the outside of my house, I have a landscaper come every week. How could they not see anything?”
Mr. Lancia said he saw Mr. Rodriguez once a month when either he or his wife came to the house to collect the rent, $1,300 a month.
The State Police said Mr. Rodriguez was a salesman at P.C. Richard in Greenvale. Ms. Kowalczik worked at a pizzeria in Farmingdale, neighbors said.
On Friday night, Major Regan said, Mr. Rodriguez was brought to a State Police station in Farmingdale for questioning. He was accompanied by a lawyer, Major Regan added, and declined to answer questions. Investigators planned to speak further with Mr. Rodriguez and Ms. Kowalczik.
“We believe that both of them have a lot of information,” he said.
This post has been revised to reflect the following correction:
Correction: October 7, 2012
An earlier version of this article and a photo caption stated that the police found the remains of a small body on Saturday. It is not clear when they were found.