Authorities in Las Vegas say they now have three "people of interest" in the abduction of 6-year-old Cole Puffinburger by men posing as police.
Officials said Saturday that they are seeking a Mexican identified as Jesus Gastelum. Police Sgt. Tom Wagner said he is believed to be in Las Vegas or Southern California.
Police also have someone else in custody, but they did not identify that person.
Cole's grandfather, Clemens Fred Tinnemeyer, 51, was arrested in Riverside, Calif., on Friday night by U.S. marshals, said San Bernardino County sheriff's spokeswoman Jodi Miller.
FBI spokeswoman Laura Eimiller said, "He was wanted for questioning in connection with the investigation but he has not been charged."
Tinnemeyer is being held on a warrant as a material witness in the federal investigation, according to the FBI.
Cole was abducted Wednesday by armed Hispanic men who posed as police officers, tied up his mother and her boyfriend, and ransacked the house, according to Las Vegas police.
On Friday, Las Vegas police said Tinnemeyer allegedly stole millions of dollars from Mexican methamphetamine dealers.
Authorities had issued an Amber Alert that triggered a public search for the boy and flashed the photo on billboards and highway signs throughout Nevada and California. The alert was called off Saturday because it helped lead to the arrest of Tinnemeyer, and its effectiveness "had run its course," Las Vegas police Capt. Vincent Cannito said.
But the hunt for Cole continued. Police concentrated efforts on a largely Hispanic neighborhood northeast of the Las Vegas Strip.
Miller said that authorities had no information about the boy's well-being.
Although trafficking-related kidnappings are relatively common in Mexico - where drug-related violence has been blamed for about 3,500 deaths this year - they rarely occur in the United States, law enforcement officials said.
Tinnemeyer purportedly owed the drug dealers $8-million to $20-million, according to the Las Vegas Review-Journal. Investigators also were looking into whether other family members might have been involved in drug operations.
Information from the Associated Press and the Los Angeles Times was used in this report.