Mr. Helbrans was found guilty of kidnapping and served two years in prison. He was released on parole in 1996 and was deported to Israel in 2000. The rabbi and his followers then established a Lev Tahor community in Quebec, Canada, in the early 2000s. After legal troubles there involving allegations of child abuse and child marriages, members of the group left Canada and eventually resettled in Guatemala.

Before the kidnapping, the children and their mother were part of the religious community in Guatemala, according to the complaint, when the mother, who is also Mr. Helbrans’s daughter, decided to leave the group and move to Woodridge, N.Y., in October of this year.

A new leader had taken charge of Lev Tahor, and the group had become more extreme, according to the complaint. The woman spoke out against changes in the group, the complaint said. Then she decided her children would no longer be safe if they stayed with Lev Tahor.

About six weeks after the move, in the early hours of Dec. 8, Yante Teller, 14, and her 12-year-old brother, Chaim, got into a vehicle in front of their home in Woodridge and were driven away. The State Police asked the public’s help in finding the children, saying they were believed to be headed to New York City.

Their ultimate destination was much farther. Mr. Rosner worked with several people across the United States, Mexico and Guatemala to try to return the siblings to the Lev Tahor community in Guatemala, the complaint said.

The children were taken to an airport outside Scranton, Pa., where surveillance footage showed them being ushered through airport security by a man whom the complaint does not identify. Days later, the children were in Mexico, the complaint said.

It remained unclear Thursday how the children were found in Mexico. The Department of Justice said it could not comment on their whereabouts. The State Police referred questions about the investigation to the F.B.I. An F.B.I. spokeswoman said the agency could not comment on nonemergency matters because of staffing plans related to the federal government shutdown.