EVANSDALE, IOWA - It's a small lake, 26 acres, an oasis of silvery blue in a place where drought and heat are burning the landscape brown.

Residents of this working-class suburb of Waterloo, Iowa, normally picnic at Meyers Lake in the shade of a wooden pavilion next to an old Army tank, or stroll the paved nature trail that circles the lake.

But in the past week, the lake has morphed from an oasis to a specter of mystery, suspicion and dread.

Here, just off the nature trail, authorities found the bikes that two girls were riding July 13 -- the day they vanished. Also on the ground was a purse one of them was carrying when, police now suspect, they were abducted.

"I don't think anybody will be coming here to relax again for a long time," said Brenda Miller, 39, who grew up in Evansdale and on Friday was among residents watching FBI sonar specialists search the lake bottom for Lyric Cook-Morrissey, 10, and her cousin, Elizabeth Collins, 8.

Police said the search, for which they prepared by partially draining the lake, was to rule out the possibility that the cousins drowned.

But they've paid attention to other possibilities too. Last week they interrogated Lyric's father, who has a criminal record and pending drug charges. They also checked the whereabouts of known sex offenders in the region, set up checkpoints to question motorists and offered a $50,000 reward from an anonymous donor.

Authorities and residents in this area of northeast Iowa about 250 miles from the Twin Cities hang onto hope that the cousins simply ran away, as Lyric threatened to do days before the pair went missing, because her dad yelled at her for not doing chores. But with every passing day, it becomes harder for people to have faith that the mystery centered on Meyers Lake will end happily.

"I hope I'm wrong," Miller said, "but I think somebody took them."

They didn't come home

The girls were last seen about 12:15 p.m. July 13, by their grandmother as they left for a bike ride. When they didn't return, a searcher found their bikes and Elizabeth's purse about 4 p.m. along the trail.

During the next few days, public safety workers and more than 1,000 volunteers on foot, in the air and on the water searched the town of about 4,500 people and parts of surrounding communities. Tracking dogs were brought in, crews dragged the lake, and authorities searched vehicles and homes whose owners consented. Local authorities called in the FBI and the National Center for Missing and Exploited Children.

Volunteers distributed thousands of posters describing Elizabeth as 4 feet, 1 inch tall and 80 pounds, with sandy hair and blue eyes, and Lyric as 4 feet, 11 inches tall and 145 pounds, with brown hair and blue eyes. And a Facebook page -- "Bring Lyric and Elizabeth Home" -- further spread the word.

Parents scrutinized

Officials said they hadn't found evidence of foul play, but it became clear early last week that they had suspicions about Lyric's father, Dan Morrissey.

He stormed out of a police interview Tuesday after investigators accused him of killing the girls. He said he was offended because it wasn't true. His family complained that police were focusing too much on Meyers Lake and the criminal past of Lyric's parents, and not enough on looking for an abductor.

Morrissey and Lyric's mother, Misty Cook-Morrissey, have a history of methamphetamine-related charges, including a pending case in which he's free on bond. He's also charged with assaulting his wife last summer.

She was released from federal prison in May after serving several years for conspiracy to manufacture and sell meth and violating the terms of her release.

The couple stopped talking to police and reporters Thursday on the advice of their attorneys, the family said. But Tammy Brousseau, an aunt of the girls, said Friday that the pair had rethought that decision. "Dan felt attacked, but after getting some rest, his mind is clear, and he's now cooperating with everyone," Brousseau said.

That about-face came on the same day authorities, with help from a sonar-equipped FBI dive team, became satisfied that the girls weren't in Meyers Lake and officially declared the case an abduction.

Another factor in that conclusion was the discovery Friday of some "evidence" police sent to Iowa's state crime lab for analysis, said Chief Deputy Rick Abben of the Black Hawk County Sheriff's Office.

He refused to say what the evidence was and said police aren't focusing on any particular person, even though a county prosecutor got a court order Friday placing Dan Morrissey in a pretrial supervision program. It requires him to report regularly to authorities while the drug charges against him are pending.

"It's been seven days, and if they were lost, they would have been found by now," Abben said. "Now that it's an abduction, everyone is a suspect until we find those little girls."

Brousseau said the families always believed it was an abduction and are glad police are on the same page. "It's frustrating," she said, "but investigators need to do what they need to do to rule things out."

Hope floats skyward

Hundreds of people from the Waterloo area -- most wearing pink shirts with the girls' pictures -- gathered Friday night in a park next to some Evansdale ballfields.

Volunteers passed out pink and purple helium balloons and markers with which people wrote messages on the balloons, including, "We will never give up" and "Come home. We miss you."

The Rev. Rick Edwards of Countryside Vineyard Church led a prayer for the girls' safe return and for the power and grace to forgive their abductor.

"We're showing this family how much we love them, how much we love these girls," he prayed. "As a community, we're going to get through this."

He then gave the word, and the balloons were released.

As the people hugged one another and craned their necks to watch, hundreds of colorful expressions of hope swarmed skyward, caught the wind and drifted out of sight.

Police ask anyone with information to call 911 or 1-319-232-6682.

The Associated Press contributed to this report. Larry Oakes • 612-673-1751