A northern New Jersey high school teacher accused of having sex with several male students is now facing a 40-count indictment.

Essex County authorities say Nicole DuFault is charged with aggravated sexual assault and child endangerment for allegedly engaging in sex acts with six victims.

Authorities say all of the boys were between 14 and 15 years old at the time the alleged incidents occurred on multiple occasions in 2013 and 2014. They say some of the sex acts occurred on school property and in DuFault's car

The indictment, handed up by a county grand jury, was made public Tuesday.

The 35-year-old Caldwell resident had been a language arts teacher at Columbia High School for several years before she was arrested last September. She remains free on $500,000 bail.

The investigation began with school officials, who then flagged law enforcement, according to the prosecutor's office last fall.

Board of Education president Elizabeth Daugherty had said in a statement that the allegations were "deeply disturbing," but declined to discuss how the investigation began, citing confidentiality rules.

Neighbors previously told NBC 4 New York Caldwell was a "sweet woman."

"I thought she was a responsible adult, taking care of the kids, raising the family, and then all of a sudden it's like, bam," said Donna Lee. "That's what's so shocking, and it's the kids who are suffering in all this."

Nancy Ursitti said Dufault is the "gentlest mother to her children."