A New York foster parent accused of repeatedly sexually abusing boys in his care kept his victims quiet by threatening them and telling them he had installed hidden cameras in his house to watch their every move, a detective on the case said.

"He told them he could hear and see everything they would do," Suffolk County Police detective Lt. Robert Donohue told The Associated Press.

The Suffolk County district attorney is trying to figure out how the foster father was able to continue getting children placed in his care despite years of concern about his conduct.

A grand jury indicted the foster father, Cesar Gonzalez-Mugaburu, earlier this month on charges that he sexually abused at least seven boys inside his split-level ranch home on eastern Long Island.

Since his initial arrest in January, other victims have continued to come forward, police said. So far, police have interviewed a dozen potential victims. Officials said he has cared for as many as 140 children.

Authorities have confirmed Gonzalez-Mugaburu was the subject of nine previous investigations involving alleged abuse dating back to 1998, each of which led to a finding that the allegations weren't credible. The last of those probes against Gonzalez-Mugaburu came in April 2015, Donohue said.

Gonzalez-Mugaburu made a practice of taking in mostly developmentally disabled boys or kids with behavioral problems, the detective said.

"He was a predator and he knew exactly the segment of the population to prey on," Donohue said. "We're dealing with vulnerable teens from broken families. Most of them are on medications and have diagnoses of behavioral or psychological problems that create a limit in their credibility."

A break came in January, when detectives said two brothers who lived in the house came forward with credible stories of abuse. Once Gonzalez-Mugaburu was in custody, others felt more comfortable about coming forward, Donohue said.

Gonzalez-Mugaburu, 59, has pleaded not guilty to a 17-count indictment charging him with child endangerment and sexual misconduct. He is accused of victimizing children as young as 8. One charge alleges he sexually abused a female dog in front of a child.

His attorney has not returned telephone messages or responded to an email seeking comment, but in a brief jailhouse interview with the New York Daily News, Gonzalez-Mugaburu said the charges are "not true."

Rose Anello, chief strategy officer for SCO Family of Services, which placed 72 children in Gonzalez-Mugaburu's care over 20 years, described many of them as having special needs. She said SCO never found reason to discontinue placing children until January.

"SCO has been working closely with the local authorities and law enforcement to better understand the scope of this matter," Anello said. She added that SCO is working with an independent, abuse-risk management organization to review the case and has stopped placing children in one of its foster programs.

She said SCO's policy is to certify foster parent homes annually. Caseworkers are expected to make home visits at least once a month. She said socio-therapists visit twice a month. Anello did not respond to questions about whether all those requirements were met in the Gonzalez-Mugaburu case, citing the ongoing investigation.

Suffolk County District Attorney Thomas Spota said Gonzalez-Mugaburu earned as much as $18,000 a month as a foster parent, caring for six to eight children at a time since at least 1996.

Spota said statute of limitations laws prevent filing charges involving some suspected victims.

In Gonzalez-Mugaburu's quiet neighborhood in Ridge, neighbors said they never suspected any trouble happening in his home, where two vintage sports cars are parked in the driveway.

"Really nothing out of the ordinary," said Christine Stean, 30. "You would see the kids raking leaves and doing yard work, but it didn't seem like anything out of the ordinary."

Matthew Roamer, 28, added: "It's just shocking. It blows your mind about what can go on two houses down that you have no idea about."

___

Follow Eltman on Twitter at @feltman41.