Elizabeth Collins, Lyric Cook-Morrissey: Search for missing Iowa cousins "at a standstill," aunt says

(CBS/AP) DES MOINES, Iowa - The search for missing Iowa cousins Elizabeth Collins and Lyric Cook-Morrissey enters its seventh day, with authorities now moving their efforts to a landfill while a congressman calls for more FBI involvement.

Pictures: Hundreds search for missing Iowa cousins

Family members of Elizabeth, 8, and her 10-year cousin, Lyric, are pleading for more help in finding the girls, who were last seen Friday. Tammy Brousseau, aunt to both girls, said the search is "at a standstill" and she fears the girls were abducted, possibly by a sexual predator.

For the third straight day Wednesday, authorities drained the lake near where the girls' bicycles were found last week in hopes of ruling out that the girls' bodies would be found underwater. Brousseau dismissed the possibility the girls might have drowned, noting they are good swimmers and their shoes weren't found.

The draining was taking longer than expected, but Black Hawk County Chief Deputy Rick Abben said he expected to wrap up by Friday with the help of equipment. Earlier in the investigation, officials dredged the lake, and on Monday night FBI dogs detected their apparent scents in the area, indicating a strong likelihood the girls had been there.

U.S. Rep. Bruce Braley said the family of the girls asked him to send a letter to FBI Director Robert Mueller, seeking assurance that all available agency resources were being used. FBI spokeswoman Sandy Breault said there was a possibility that a dive team from Los Angeles may be deployed to search the deeper holes of water in the lake.

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

Complete coverage of the missing Iowa cousins on Crimesider