(CNN) -- Searchers are using scent dogs as they look for any signs of two young girls who were last seen on Friday, riding their bikes near a lake in Evansdale, Iowa.
The FBI brought two dogs to the area Monday night, and the dogs may be used again on Tuesday, FBI spokeswoman Sandy Breault said.
The girls -- 8-year-old Elizabeth Collins and 10-year-old Lyric Cook -- were last seen by their grandmother on Friday when the two, who are cousins, left to go on a bike ride, authorities said.
The dogs used scent pad samples taken from the girls' shoes and did pick up a scent trail, but Breault couldn't say what, if anything, it led investigators to.
"We just want our girls home," Tammy Brousseau, an aunt to both girls, told CNN's "AC360." "We're bracing for the worst, but hoping for the best."
Sitting beside Brousseau during the interview was Misty Cook-Morrissey, Lyric's mother. She said she wanted people to know what the girls are like.
"They're very outgoing. They're very sweet, talkative, they're fun. They smile a lot. They're pretty persistent in the things that they want. They're great, they're really great," she said.
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A massive volunteer search over the weekend failed to locate the girls, and authorities have suspended the volunteer effort.
"Are we going to get answers? I'm not sure," Lyric's father, Daniel Morrissey, told HLN's Jane Velez-Mitchell. "It's just baffling to try to figure out the pieces to the puzzle. Looking at it, it doesn't make any sense."
"It's just been a nightmare," he said. "It's been a challenge to hold everything together and continue to just keep believing and praying and trusting God that he's got this."
Brousseau, the aunt, also spoke to HLN, saying she believes her nieces must have been taken by a stranger.
"It's as though they disappeared into thin air in broad daylight," she said.
Authorities began dragging Meyers Lake over the weekend for any sign of the girls. Their bicycles were located hours after they were reported missing near that lake. The search remains a missing persons case.
"We really have nothing new that I can tell you, other than the fact the search is continuing," Rick Abben, chief deputy for the Black Hawk County Sheriff's Office, told reporters Monday. "... We're still looking for both of them. There's no new evidence or anything that's been found."
Nearly 1,000 volunteers helped in the search Saturday, and nearly 900 on Sunday, he said.
Calls are coming in to a tip line, he said, and each bit of information is being checked out. Police ask that anyone who may have seen the girls on Friday contact authorities.
Abben said the volunteer effort was suspended because authorities did not feel there was a benefit in having more people search. However, he said, "we can always call those folks back out."
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Agents from the FBI and the Iowa Department of Criminal Investigation joined the search on Saturday, authorities said.
Abben told reporters Monday there was no indication the girls were outside Evansdale, a town of about 4,700 located about 12 miles southeast of Cedar Falls. Nor was there any indication of foul play, he said.
"It's like they vanished," he told CNN affiliate KWWL. "There's just nothing."