Story highlights Authorities went to check on the welfare of a 6-year-old child in Farmingdale

The child's mother said another child had died, but his death wasn't reported

"Infant remains" are found in the backyard of the home the couple shared

Authorities have discovered the remains of an infant in the backyard of a Long Island home after child protective officials were sent this week to check on the welfare of a 6-year-old.

While they did not positively identify the recovered infant, New York State Police said Saturday that the woman who lives in the home told investigators that the death of one of her children had not been reported. The boy, named Justin Kowalczik, would now be around 3 years old.

"This interview also revealed a possible location of Justin's remains," police said of their talks with Heather Kowalczik.

Based on the interview, authorities obtained a warrant to search the family's property.

"It is absolutely a suspicious death," New York State Police Major Patrick Regan told reporters, saying authorities "believe the child was there since approximately July of 2010."

The woman's boyfriend was identified by police in a news release as "a person of interest" in the case. A state police spokesman could not be reached Saturday for further comment. No charges have been filed.

"The Medical Examiners Office is conducting their investigation and the State Police are waiting for the confirmation of the identity and cause of death of the remains found," police said in the news release.

The couple lived together in a two-story house in Farmingdale, a Long Island community about 35 miles east of New York City.

According to police, they "parented" the 6-year-old child whom Suffolk County Child Protective Services employees had gone to check on earlier this week.

It was during that investigation that authorities learned Justin Kowalczik, who was born in 2009, "was unaccounted for."

Meanwhile, a 9-year-old child of Heather Kowalczik and her boyfriend was briefly sought by authorities after he didn't show up for school Friday. Authorities said the boy's father had driven off with him. Both were later found, state police said.