Elizabeth Collins and Lyric Cook: Parents of Missing Iowa Cousins Remain 'Hopeful'

July 23, 2012 — -- Despite a fruitless 10-day search for two missing Iowa cousins, the parents of one of the girls, 8-year old Elizabeth Collins, have not lost hope, bolstered by authorities' saying they believe the children are still alive.

"They told us they do have a couple of leads and that is it. Anything is hopeful," Heather Collins told ABC News' Robin Roberts today in an exclusive interview on "Good Morning America."

Elizabeth and 10-year old Lyric Cook vanished July 13, but authorities made a surprising announcement this weekend.

"We believe these girls are alive," FBI spokesperson Sandy Breault said Saturday.

Investigators want to hear from anyone who might have been near the trail where the girls' bikes were found the day they disappeared.

"Even if you think you don't have any information that's important to this case, investigators want to talk with you," Breault said Sunday. "Don't assume we know what you know."

Investigators for the first time said they are pursuing people of interest in the case. But they said they are not receiving full cooperation from all the family members.

After initially cooperating and taking polygraph tests, Lyric's parents, Misty and Dan Morrissey, elected not to allow police to interrogate them any further, stating that the decision came on advice from their attorney. They have been convicted of felony drug charges in recent years and served time behind bars.

Tammy Brousseau, the girls' aunt, told ABC News that something in the Morrisseys' past might have played a role in their disappearance.

"I can't rule that out, you know," she said. "I want every stone unturned."

Heather Collins said Monday she wants the focus to be on the missing girls, not her sister's past, but she understands the need for investigators to look at other issues as well.

"When they don't have full cooperation, their focus has to be on other issues rather than on the girls being found home. That's our main concern. That's our main focus - is bringing the girls home. And that's all we want," she said. "They don't need other distractions. They have enough to worry about and they don't need other distractions."

Elizabeth and Lyric disappeared after leaving for a bike ride around noon July 13. Their bikes were soon found by Meyers Lake. Authorities called in an FBI dive team late last week that searched the lake and determined that the girls were not in it, prompting them to call the case an abduction.

Now, as the small town desperately waits for answers, the parents hope this nightmare will soon come to an end with their girls back home. Both Heather Collins and her husband, Drew, urged whoever has the cousins to let them go.

"Take them somewhere safe," she said. "Take them to a gas station, Target. Just take them anywhere so that they know how to get a hold of somebody to get a hold the police or their parents so that they can get home safe and bring them back. We miss them dearly."