( CNN ) -- The mother of a missing Iowa girl thinks there is a chance she and her cousin were abducted and are not at the bottom of a lake where dogs have led searchers . `` Because we have n't found them anywhere in the surrounding area , I feel like maybe they were taken , '' Misty Cook-Morrissey , mother of 10-year-old Lyric Cook , told CNN on Wednesday . Lyric and 8-year-old Elizabeth Collins were last seen by their grandmother on Friday when they left on a bike ride . Missing girl 's grandma : 'We will fight ' The girls ' bicycles and a purse were found near Meyers Lake hours after they were reported missing . Scent dogs following the girls ' trail led searchers around the lake and stopped at the water 's edge , Cook-Morrissey said . Authorities are draining the lake , but the operation is taking longer than originally expected . Officials expect the lake to be drained by Friday , said Chief Deputy Rick Abben of the Black Hawk County Sheriff 's Office . Mom : Dogs searching for Iowa girls stopped at edge of lake . But Cook-Morrissey said the girls do n't go to the lake . `` They do n't swim there . My daughter is familiar with swimming in lakes , so I do n't think she would be scared of this lake , but they do n't come here and swim here , '' she said . Cook-Morrissey said she 'd be `` more comfortable '' with the theory that the girls might have been abducted `` once they drain the lake and we find nothing there . '' `` If you 've taken our kids , '' she said on national TV , `` bring them back . '' The FBI brought two dogs to the area to search Monday night , spokeswoman Sandy Breault said . Authorities did all they could with the dogs , and the animals wo n't be used again unless there is a new development , she said . Authorities said Tuesday that they did n't know whether the girls had been at the lake . `` We have their bicycles , and we have the purse , and that does n't tell me that they 've been there , just that those items are there , '' Abben said . The family has been questioned and polygraphed and had information taken from their cell phones , a process Cook-Morrissey said is hard but necessary . `` We know that it 's a necessary measure they have to take to get as much information as they can and of course rule us out , so we did what we have to do , '' she said . Questioning has taken Cook-Morrissey and other family members away from the lake , which is hard , she said . `` Not that being out here might make a difference , but in your heart you want to be close to where they were last seen , '' she said . When Deutsch heard that two little girls were missing in his town , he said , the first thing he did was to make sure every city asset that was needed was made available to the county sheriff . Family 'bracing for the worst but hoping for the best ' The next thing he did was take to the air , taking off in his twin-engine plane and flew over his town , looking for any sign of Lyric and Elizabeth . `` It just makes you sick , '' said Deutsch , who knows both families . In this town , neighbors know exactly how many people live there -- 4,751 -- and the small community has never suffered through anything like the worrying going on now , the mayor said . The search remains a missing persons case , authorities said . No evidence has been found to suggest this is a crime , Deutsch said , but it is a mystery that has the whole community looking for two of their own . `` We just want our girls home , '' Tammy Brousseau , an aunt to both girls , told CNN 's `` AC360Ëš . '' `` We 're bracing for the worst but hoping for the best . '' Calls are coming in to a tip line , Abben said , and each bit of information is being checked out . Police ask that anyone who may have seen the girls on Friday contact authorities . Lyric 's grandmother Wylma Cook said she does n't believe that the girls intended to go swimming . `` I do n't think they would have even known the way to Meyers Lake , '' she told HLN 's Nancy Grace on Tuesday . Heather Collins , Elizabeth 's mother , told HLN 's Jane Velez-Mitchell that if the girls were abducted , she would not pass judgment . `` We just want our children brought back , '' she said .
NEW : Officials expect the lake to be drained by Friday . Mother says the family has been polygraphed , which is hard but necessary . They are being held in a jail cell for now until they can get out of there and go home. Scent dogs ran around the lake and stopped at the water 's edge .