Missing Iowa Cousins: Cops Begin Draining Lake in Search for Girls

Heather Collins is staying focused on being reunited with her girls.

"We love you. We want you back home," she said, choking up. "We miss you guys. Everybody misses you. We're all going to have a huge party when you get back home."

Police are working with federal authorities on what to do next.

"Every hour, you know, it makes it that much worse. The first 24 hours of course are very critical. We've obviously surpassed that now by quite a bit," Abben said.

No Amber alert was issued in the case, because it does not meet the requirements, Abben said.

Family of Missing Cousins Refuse to Give Up Hope

"Because we have no person that was seen and we have no vehicle that was described, so we can't issue an Amber alert by their guidelines," Abben said.

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The girls' grandmother, Wylma Cook, says she fears they were abducted.

"Whoever has them, just turn them in, let them loose anywhere so they can call me," Cook said. "Lyric knows my cell phone, she knows my house phone."

Tammy Brousseau, Cook's aunt, says she knew what to do if a stranger approached her.

"I taught her myself if they got a hold of your arm, drop to the ground, kick, bite, scream, do everything you can," said Brousseau.

More than 1,000 volunteers have fanned out around the area to look for the girls. The response was so overwhelming that when hundreds of volunteers showed up Sunday, search organizers said it took several hours to bus people to assigned areas. Neighbors in this small, tight-knit community say it's the least they could do to help.

"I have two little girls at home. Just want to bring them home safe to their mommy and daddy," said volunteer Kim Einfelt. "Can't lose hope. Can't."

ABC News' Olivia Katrandjian and ABC News Radio contributed to this report.