A couple who are charged with kidnapping two Amish girls in northern New York intended to keep them as “slaves”, an investigator said Thursday.

The Associated Press reports that Nicole Vaisey admitted she and her boyfriend, Stephen Howells Jr., lured the girls into a car by promising to allow them to pet a dog that they had with them.

St. Lawrence County Sheriff's Detective Sergeant Brooks Bigwarfe testified at Vaisey's preliminary hearing, saying that she “called it a shopping trip and they wanted to make the two girls their slaves.”

Brooks added that once they were taken to the couple's home, the girls, aged 7 and 12, were "handcuffed together at the ankles and handcuffed to the bedpost because [Howells and Vaisey] were scared they were going to go out the window and flee the house," according to WYNY News

The girls' abduction sparked an Amber Alert in the area when they were abducted Aug. 14. CBS News reports that the couple released the girls after being frightened by news reports about their abduction.

Prosecutors subsequently revealed that the pair had been sexually abused during their captivity. 

Fowler Justice Paul Lamson ruled Thursday there was reasonable cause to believe Vaisey committed felony kidnapping. He ordered her held without bail. Howells, who is has been in custody since his arrest Aug. 15, waived his right to a hearing.

Earlier, St. Lawrence County Sheriff Kevin Wells told reporters that investigators were looking to ascertain whether the couple had been involved in other kidnappings or abuse, saying that there was "definitely potential" that Howells and Vaisey attacked others prior to last week's kidnapping, according to NCPR