RIVERHEAD - A Ridge foster father was arraigned on new charges Thursday for allegedly sexually abusing children in his care.

As News 12 Long Island reported in March, Cesar Gonzalez-Mugaburu, 60, was indicted on charges that he sexually abused seven of his foster children.

Suffolk County District Attorney Thomas Spota says six more foster children have come forward since he was first indicted, prompting new charges against Gonzalez-Mugaburu.

He pleaded not guilty in Riverhead court.

Officials say as many as 140 children were placed in his care over a span of 20 years. The majority of them were developmentally disabled boys.

Defense Attorney Donald Mates called the new allegations against his client "lies" and says Gonzalez-Mugaburu maintains his innocence.

Spota says his office has convened a special grand jury to investigate "serious flaws in the foster care system."

Several foster care agencies and some of the alleged sexual abuse victims have already testified in front of that grand jury. It's not expected to wrap up the investigation until early 2017.

Spota did not comment when asked whether he thought any of the foster care agencies that placed boys with Gonzales-Mugaburu are complicit in any crimes.