The grandfather of a 6-year-old boy who was abducted for four days was due in federal court Monday to face a racketeering charge, the U.S. Attorney's office said.

Clemens Fred Tinnemeyer, 51, and a woman described as his companion, Terri Leavy, 42, have been held as material witnesses in California since their separate arrests in the kidnapping investigation. Cole Puffinburger was abducted Oct. 15 and found unharmed late on Oct. 18 on a Las Vegas street.

Tinnemeyer and Leavy were to appear before a federal magistrate on charges of interstate and foreign travel or transportation in aid of racketeering enterprises, said Natalie Collins, spokeswoman for U.S. Attorney Gregory Brower.

Las Vegas police have characterized the boy's abduction as a message from "Mexican nationals" and methamphetamine traffickers aimed at Tinnemeyer, who police alleged made off with millions of dollars in drug money. Police said two gunmen posing as police officers tied up the boy's mother and her boyfriend and ransacked their home before taking the boy.

Tinnemeyer was arrested Oct. 17 in Riverside, Calif. Leavy was arrested Oct. 19 in Fontana, Calif.