A man is wanted for questioning, and police are searching the northeast part of the Las Vegas valley for a kidnapped 6-year-old boy whose grandfather — allegedly a Mexican drug lord — was arrested late Friday in connection with the case.

An Amber Alert for the boy, Cole Puffinburger, was canceled midday Saturday, but Las Vegas Metro Police Capt. Vincent Cannito told reporters that authorities hadn't given up the search.

"The number of tips that we have been receiving over the Amber Alert line has slowed considerably," Cannito said, explaining the reason for focusing on other avenues in the investigation.

Cannito also said that a number of search warrants were executed in jurisdictions "throughout the country," yielding significant evidence, including case. And he released a photo of a Mexican man identified as Jesus Gastelum wanted for questioning as a "person of interest" in Puffinburger's disappearance. Two other "people of interest" people already have been questioned.

One is Puffinburger's grandfather, Clemons Fred Tinnemeyer, 51, who was arrested Friday night by federal agents near Riverside, Calif., though it wasn't immediately clear what charges he might face.

Los Angeles FBI spokeswoman Laura Eimiller told FOXNews.com that Tinnemeyer was arrested on a federal material witness warrant.

Police think Tinnenmeyer, of Las Vegas, conducted drug deals with Mexican nationals, from whom he may have stolen millions of dollars, Officer Cris Johnson, a Las Vegas police spokesman, said. And Cannito said the boy's abduction on Wednesday was a "message" of retaliation against the grandfather.

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Tinnemeyer is being held at the Central Detention Center in the city of San Bernardino, Calif., and is listed on the San Bernardino County Sheriff's Web site as ineligible for bail.

Cole was snatched from a Las Vegas home by two fake policemen, who tied up the child's mother and her boyfriend at their house Wednesday morning.

Cannito said the two Hispanic men who carried out the kidnapping were after "significant money and drugs."

Johnson declined to say what role Tinnemeyer played in the drug operation or whether the kidnappers were seeking a ransom. Police believe methamphetamine was involved, Johnson said, and the Las Vegas Review-Journal characterized the illicit operation as a multimillion-dollar Mexican drug ring.

Authorities also were investigating whether other family members had ties to the drug operation, Johnson said.

"Money is a huge factor, obviously. Drugs are a huge factor," Johnson said. "The only innocent person involved in this entire operation is the boy."

FOX News' Adam Housley, Catherine Donaldson-Evans and The Associated Press contributed to this report.