BOSTON -- U.S. Immigration officials have now joined FBI agents trying to determine the true identity of Clark Rockefeller, a man charged with kidnapping his young daughter from Boston.

They are trying to determine whether Rockefeller, 48, is actually a German exchange student who came to the U.S. more than 25 years ago and who has been linked to the mysterious disappearance of a California couple in the 1980s.

Los Angeles County Sheriff's department traced Rockefeller's fingerprint to a Chris Chichester, whose fingerprint was recorded on a stock broker's license application, two law enforcement sources told ABC News.

The fingerprint given in the name of Chichester also matched the name of a German student, Christian Streiter, according to ABC.

Rockefeller was arrested in Baltimore Aug. 2 and charged with kidnapping and assault and battery after allegedly abducting his 7-year-old daughter Reigh "Snooks" Boss during a supervised custody visit.

Police now want to question him in connection with the 1985 disappearance of a California couple Chichester once rented from, but Rockefeller refused to talk to them. Detectives said they were returning to the Golden State Thursday to continue investigating the case.

FBI agents Wednesday interviewed a Connecticut family who hosted an exchange student named Christian Gerhart Reiter or Streiter more than 25 years ago, according to the Boston Herald.

Members of the Savio family in Berlin, Conn., said FBI agents interviewed them about Reiter, who lived with them for a few weeks and made the family uncomfortable because he looked down on their middle-class lifestyle.

“He made my mom really nervous,” Edward Savio, 45, told the Herald. “He said he was from Bavaria. We were a modest, middle-class family and he would say things like, ‘I would never live like this.’

He finally moved out after an incident in which he locked a Savio child out in the cold for several hours, but Savio said his mother continued to get calls from Reiter after he left and he told her he had moved to California.

She didn't hear of him again until FBI agents contacted her in the 1990s about the disappearance of San Marino, Calif., couple Linda and John Sohus, he said.

They asked her what she knew about a man named Christopher Crowe, who had tried to sell a truck in Connecticut that belonged to Sohus.

A Christopher Chichester had rented an apartment from the Sohus couple. Chichester was also the surname of a Berlin high school teacher who Reiter especially liked, according to the Herald.

A former librarian at the Berlin high school also befriended Reiter and said he ran up a big long-distance phone bill that he was forced to pay back by the school principal. She said she was later told that he came from humble origins in Europe, his father a house painter and his mother a homemaker.

The German consulate in Boston said it had also been contacted by the FBI Wednesday, with agents asking for information about a German citizen named Christian Gerhard Streiter, according to the Boston Globe.

The Foreign Ministry in Berlin confirmed to ABC News that U.S. law enforcement agents have asked the German embassy to help with the Rockefeller investigation, and the German tabloid Bild Zeitung published his photo in its Munich edition.

Rockefeller's attorney, Stephen Hrones, said Rockefeller can't remember anything before his 1993 marriage to Sandra Lynn Boss, Reigh's mother, to whom he was married for 13 years before a 2007 divorce. Boss works for a management consulting firm in London.

Rockefeller lost custody of his daughter during 2007 divorce proceedings after refusing to reveal his true identity.

Sources told the Boston Globe that Rockefeller claimed in divorce court to have lost his memory and become a mute after his parents' death when he was a child. He said he was raised by an uncle in New York and home-schooled, which was why he had no school records.

Hrones said Rockefeller did live in California at some point, but he disavows any knowledge of the Sohus case and has insisted his name is Rockefeller. The well-known and wealthy American Standard Oil Co. Rockefeller family said he is not part of their clan.