(CNN) -- A woman was arrested in connection with the abduction of 6-year-old Cole Puffinburger from his Nevada home last week, the FBI said Monday.
Terri Leavy, 42, is believed to be the companion of Cole's grandfather, Clemens Fred Tinnemeyer, 51.
Both were wanted on federal material witness warrants issued in Las Vegas, Nevada, related to Cole's disappearance last Wednesday from his Las Vegas home, authorities said.
Fontana, California, police arrested Leavy Sunday night, an FBI spokeswoman said.
A federal magistrate in Riverside on Monday ordered the pair detained by U.S. Marshals and returned to Las Vegas, where they face questioning under the warrants, said FBI spokeswoman Laura Eimiller.
No charges have been filed in the case.
Cole was found Saturday night, three days after armed men took him from his home in what police are calling a drug-related kidnapping.
A bus driver picked up Cole as he was wandering alone down a sidewalk in Las Vegas' east side.
Julio Diaz said Cole asked for a ride and "was never shy to ask for help."
"I realized it was a police matter. Something was not right, and I would have to find out what was going on with that boy," said Diaz, who told reporters that he didn't immediately recognize the boy.
Cole was reunited with his family after medical checks, Capt. Vince Cannito of the Las Vegas Metropolitan Police Department said Monday.
"He was in good shape; he was extremely healthy," Cannito said.
Tinnemeyer was arrested in Riverside in connection with the warrant from Las Vegas, where police are focusing on a possible drug link to Cole's abduction. Watch what police hoped arrest might mean »
Citing sources and police, the Las Vegas Review-Journal newspaper has reported Tinnemeyer may have stolen millions from a Mexican drug cartel, although police have not said what role he may have played in the drug operation or whether the child's abductors were seeking a ransom. Officer Cris Johnson told the newspaper authorities believe methamphetamine was involved.
"The remainder of the investigation now shifts, the focus now goes on to the drug dealing and potential extortion," Cannito of the Las Vegas Metropolitan Police Department said Sunday.
Before his arrest, police said Tinnemeyer was involved in "significant drug dealing" involving millions of dollars.
Cannito had said earlier that Cole was kidnapped by drug dealers attempting to recover lost money and property.
Three armed men, some posing as police, snatched the boy Wednesday after they tied up his mother and her fiance and ransacked the home, officers have said.
Cole's father, Robert Puffinburger, said the emotion he felt after being informed that his son was safe was "indescribable."
"I'm just glad he's safe," Puffinburger said at Sunday's news conference, his voice breaking. "I can't wait to see him!"
The boy's disappearance sparked a mass hunt around Las Vegas, Nevada, and a nationwide Amber Alert.
A large amount of cash and evidence have been recovered in several jurisdictions, Cannito said. He gave no further details.
Also, authorities are seeking a man for questioning called Jesus Gastelum, Cannito said Saturday.