Credit: ABC News

Police and hundreds of volunteers are dragging a lake and fanning out across the Evansdale, Iowa, area, searching for two Iowa girls who haven't been seen for two days.

Elizabeth Collins, 8, and her cousin, Lyric Cook, 10, were last seen around midday Friday, riding their bicycles in downtown Evansdale, Iowa.

Police say they found the girls' bicycles and a bag they were carrying on a trail near Meyers Lake. Crews used boats to search the lake and volunteers looked in the woods Saturday and were back today, but haven't found what happened to the girls.

"We will keep searching until we are confident that they are not in that lake," Captain Rick Abben, a chief deputy with the Black Hawk County Sheriff's Office, told ABC News affiliate KCRG.

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

"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.

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.

"I thought with the helicopters and my other son and a friend going on four-wheelers until four o'clock in the morning they would see all these lights and stuff or something," Cook told KCRG. "When I woke up this morning, I just bawled my eyes out."

An anonymous person has offered a $5,000 reward for information leading to the girls' whereabouts, police said.

ABC News Radio contributed to this report.