IOWA CITY, Iowa — The grandmother who was babysitting two Iowa cousins when they disappeared nearly two weeks ago after going for a bike ride said Tuesday that she has no idea how they ended up across town by a lake.

Wylma Cook, 72, said that Lyric Cook and Elizabeth Collins occasionally went biking while she babysat them several days a week at Collins' parents' home in Evansdale. But she said they almost always stayed within blocks and had never gone to Meyers Lake, a mile away.

"It shocks me, OK. The girls never rode that far, never. It was in a two-block area, that's it. They always returned like I told them," Cook said.

Authorities found the girls' bikes and a purse on a path near the lake July 13, hours after they were reported missing in Evansdale, a northeast Iowa town of 4,700. FBI bloodhounds picked up on the girls' apparent scent near the lake last week and investigators have ruled out the possibility of drowning.

An extensive search involving local, state and federal investigators has failed to find them. FBI spokeswoman Sandy Breault said there was "nothing new" about the case Tuesday.

Breault stood by her assertion, first made Saturday, that investigators believe the girls are alive.

"They are not going to reveal the reasons why. You wouldn't want them to do that. It would jeopardize the investigation and the children," she said.

David Finkelhor, director of the Crimes Against Children Research Center at the University of New Hampshire, said that claim means investigators could "have something quite important" for evidence. He said cases of two children being abducted by a stranger were rare since it would be hard for one person to control both, which makes the common motive of sexual gratification less likely in this case.

He said it makes sense to look into whether the abduction is linked to pending drug charges against Daniel Morrissey, Lyric's father, a habitual felon facing decades in prison on charges of conspiracy to manufacture methamphetamines. In other cases, children have been kidnapped by rivals out of retaliation or held hostage to prevent incriminating testimony, he said.

"If they do think the dynamics are primarily around the drug cases, investigators might be more likely to think the girls are alive. They lose their value if they have been murdered," he said.

Court records show Morrissey, 36, appeared in court for a change of plea hearing in one of his drug cases the day before the kids vanished but did not plead guilty. Prosecutor Brad Walz said such hearings usually indicate a guilty plea is forthcoming, but declined comment on why Morrissey did not enter one.

David Mullin, a defense attorney for Jason Stolfus, who was arrested with Morrissey and faces the same charges, said the prosecutor told him Morrissey's plea agreement "fell through." He said police reports show Morrissey implicated his client in crimes after both were arrested in December. But he said Stolfus would not have a motive to take the children because he has been offered a favorable plea deal in which he would likely avoid prison.

"The consequences will be so little that it would hardly be a motive to witness tamper or anything like that," Mullin said. The charges against Morrissey, on the other hand, carry 45 years in prison apiece because he is a repeat offender.

Cook, the girls' grandmother, said she doubted the abduction was linked to drugs but could not rule it out. She said Dan Morrissey voluntarily turned his cellphone over to investigators in recent days and explained all the calls he made and received.

"I mean there could be a side chance of somebody that hates him or something, I don't know," she said. "Everybody is being checked out."

Cook said she is "praying so hard" for the girls' safety while picking over the details of the day she last saw them, when they left for a bike ride at 11:30 a.m.

Cook said Lyric knew she had to return home shortly because Lyric and Cook planned to leave for the home they shared in nearby Waterloo with Lyric's mother, Misty Morrissey, by 1:30 p.m. Cook said she expected the girls to return for lunch or a drink of water or juice as they always did when they were playing in the heat.

"That's what's just so strange about all of it," she said.

Cook said she got nervous when they weren't back by 12:30 p.m. and started driving around town looking for them. After an hour of searching, she returned to the home. Cook said that Misty Morrissey stopped by after getting off work.

"Misty said, `Mom, you go home and I'll just wait for Lyric and bring her home," Cook recalled.

Cook said she drove to her home but was soon told by Elizabeth's father the girls hadn't surfaced. A firefighter found the bikes two hours later, and the manhunt began.

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  • Lyric Cook, Elizabeth Collins

    This combo made from undated photos provided by the FBI shows cousins Lyric Cook, 10, right, and Elizabeth Collins, 8, who have been missing since Friday, July 13, 2012. Dan Morrissey, Lyric's father, is expected to learn Friday, July 27, whether he will be put on trial next week for domestic abuse or drug charges, raising the possibility that he could be sent to prison even as the search continues. (AP Photo/FBI)

  • Elizabeth Collins

    This photo provided by the FBI shows Elizabeth Collins, 8. Collins and her 10-year-old cousin Lyric Cook, who have been missing since Friday afternoon, July 13, 2012, when they went for a bike ride in Collins' neighborhood in Evansdale, Iowa. Their bikes were found a mile away near a lake, and investigators say they have no idea what happened to them. (AP Photo/FBI)

  • Lyric Cook

  • Elizabeth Collins, Lyric Cook-Morrissey

  • Misty and Dan Morrissey speak to the media near Meyers Lake where their daughter Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, disappeared last Friday, Tuesday, July 17, 2012, in Evansdale, Iowa. The girls' bikes were found Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)

  • Misty and Dan Morrissey walk to speak to the media near Meyers Lake where their daughter Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, disappeared last Friday, Tuesday, July 17, 2012, in Evansdale, Iowa. The girls' bikes were found Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)

  • Dan Morrissey leans on a tree near Meyers Lake where his daughter Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, disappeared last Friday, Tuesday, July 17, 2012, in Evansdale, Iowa. The girls' bikes were found Friday afternoon near a bike trail at the edge of the lake. (AP Photo/Charlie Neibergall)

  • Elizabeth Collins

    This undated photo provided by Black Hawk County police shows 8-year-old Elizabeth Collins, who, along with her 10-year-old cousin Lyric Cook-Morrissey, has been missing since Friday afternoon, July 13, 2012. The girls were last seen Friday afternoon leaving their grandmother's house. (AP Photo/Black Hawk County Police via Waterloo Courier)

  • This undated photo provided by Black Hawk County police shows 10-year-old Lyric Cook-Morrissey who, along with her 8-year-old cousin Elizabeth Collins, has been missing since Friday afternoon, July 13, 2012. The girls were last seen Friday afternoon leaving their grandmother's house. (AP Photo/Black Hawk County Police via Waterloo Courier)

  • Sarah Staebell ties pink ribbons for Cook-Morrissey and Collins. (AP Photo/Waterloo Courier, Brandon Pollock)

  • Police officers check a lower-level door of a business in Evansdale Monday, July 16, 2012 in the continuing search for Lyric Cook-Morrissey, 10, Elizabeth Collins, 8, who disappeared in Evansdale last Friday, July 13. (AP Photo/Waterloo Courier, Brandon Pollock)

  • An off-duty Cedar Rapids police officer searches the underbrush for clues to the disappearance of Lyric Cook-Morrissey and Elizabeth Collins along the bike trail around Meyers Lake in Evansdale Monday, July 16, 2012. The two girls have been missing since leaving their grandmother's house Friday afternoon. (AP Photo/Waterloo Courier, Brandon Pollock)

  • This photo provided by the FBI shows Elizabeth Collins, 8. Collins and her 10-year-old cousin Lyric Cook have been missing since Friday afternoon, July 13, 2012, when they went for a bike ride in Collins' neighborhood in Evansdale, Iowa. Their bikes were found a mile away near a lake, and investigators say they have no idea what happened to them. (AP Photo/FBI)

  • A poster with photos of Lyric Cook-Morrissey, 10, and Elizabeth Collins, 8, who disappeared in Evansdale last Friday, adorn a utility pole across from the entrance to Meyers Lake in Evansdale, Iowa, Monday, July 16, 2012. Their bikes were found Friday afternoon near a bike trail at the edge of Meyers Lake in Evansdale. (AP Photo/Waterloo Courier, Brandon Pollock)

  • Evansdale code enforcement officer Rick Reuter watches as Meyers Lake is drained while authorities continue to search for 10-year-old Lyric Cook-Morrissey and her cousin, eight-year-old Elizabeth Collins, who disappeared last Friday, July 13, 2012, in Evansdale, Iowa. (AP Photo/Waterloo Courier, Matthew Putney)