EVANSDALE, Iowa — The families of two missing Iowa cousins say their worry that the young girls might have been abducted is growing as a search of nearby lake winds down.

Authorities drained the lake Tuesday after FBI dogs detected the girls’ scent near where their bicycles were found four days earlier.

FBI spokeswoman Sandy Breault said the reaction from the dogs Monday night indicated a “strong possibility” the girls had been at the lake, less than a mile from their grandmother’s house where they were last reported seen Friday. However, Breault said because there were no confirmed sightings at the lake, authorities couldn’t be certain.

Chief Deputy Rick Abben of the Black Hawk County Sheriff’s Office said the case was still considered a missing persons investigation. The decision to drain the lake was made to rule out the possibility the girls were in the water, he said.

Officers slowly paddled around the lake in kayaks on Tuesday morning. A group of three officers walking along the southeast shoreline stopped to study something that appeared to be a cup. An officer with gloves and an evidence bag picked it up and took it back to a patrol car sitting along the bank.

Officials didn’t identify the object or even confirm whether it was related to the search for Elizabeth Collins, 8, and Lyric Cook-Morrissey, 10, but it was a rare sign of activity in a massive search that has produced few if any significant leads.

“I don’t think that they’re in the lake, not at all, but it is just like a dead end as far as we know so far,” said Dan Morrissey, Lyric’s father. “We’ve never gone through anything like this. It’s hard enough just to get up and deal with the reality that your daughter is gone.”

Tammy Brousseau, 48, an aunt to both girls, said all the signs were pointing to a stranger — possibility a pedophile — abducting them from the area near the lake where their bikes were found.

Brousseau said that just last week she taught Lyric how to “save someone if they went limp in the water.” She said she also taught both girls how to “drop to the ground and fight” if someone tried to abduct them.