Black Hawk County Chief Deputy Rick Abben said Thursday that authorities expect 100 percent cooperation from Misty and Dan Morrissey, parents of 10-year-old Lyric Cook-Morrissey.

Lyric and her cousin, 8-year-old Elizabeth Collins, didn't return from riding bicycles Friday in Evansdale in northeast Iowa.

Family members told the Des Moines Register that police suspect Dan Morrissey is behind the disappearance of both girls, a claim he denies. Tensions between Morrissey and investigators led him to storm out of an interview Tuesday, they added.

"They have accused [Dan Morrissey.] They said they have evidence,” Tammy Brousseau, Lyric's aunt, told the newspaper.

Both Morrisseys have spent time in prison on drug charges. Abben says background checks were done on all family members, and they have taken lie-detector tests.

Court records show that Dan Morrissey is awaiting a trial in September on drug arrests from 2011, the Des Moines Register reports.

Misty Morrissey was sentenced in 2003 to four years in prison on methamphetamine-related charges. She left prison on a supervised release but served a second, five-month sentence for a violation.

A dive team using sonar equipment searched Meyers Lake on Thursday for evidence of the cousins, an FBI spokeswoman said.

Brousseau said she feared the girls were abducted, possibly by a sexual predator. She dismissed the possibility that the girls might have drowned in the lake, noting they are good swimmers and that their shoes weren't found.

Debbie Acklin, of Black Hawk County Waste Disposal, said authorities asked the company Monday to start dumping trash from Evansdale homes and businesses in a separate area of the county landfill. Abben confirmed the landfill had been searched but declined to say what, if any, evidence was found.

Brousseau said officers recently went into a family home and confiscated all the computers "for the purpose of seeing what information they could get off them." She did not say whose home the computers were taken from, and investigators did not comment on the removal of items from family members' homes.

Drew and Heather Collins, the parents of Elizabeth, have moved from their home in Evansdale to an undisclosed location to get rest because too many people kept showing up, Brousseau said.

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