FBI spokeswoman Sandy Breault said authorities "feel strongly" that 10-year-old Lyric Cook-Morrissey and 8-year-old Elizabeth Collins have not been killed. She refused to say what led authorities to that conclusion, but urged anyone with information about their disappearance to contact law enforcement.
"We believe these girls are alive, and we are not discouraged by the passage of time since their disappearance," Breault said. "We are urging anyone with information to come forward. Any information, as insignificant as it may seem, could be vital to this investigation."
The announcement came a day after authorities finished searching Meyers Lake in the northeast Iowa town of Evansdale, which is near a path where the girls' bikes were found. The girls vanished July 13.
They now say they believe the girls were abducted, but that searching and draining part of lake was part of a thorough investigation.
"We have to cover everything," Breault told The Associated Press after Saturday's news conference. "If there's even a chance (the girls were in the lake), we have to make sure."
The lake is close to Interstate 380, just outside of Waterloo, which is about 120 miles northeast of Des Moines.
Breault said investigators are interviewing multiple "persons of interest" in the case, whom she declined to identify. She said authorities are still receiving tips on the case, mostly from within the area.
Authorities have said they are watching Lyric's father, Daniel Morrisey, although they have not named him as a suspect.
Morrisey, 36, has a long criminal history and has stopped cooperating with police. Breault said the lack of cooperation from some family members has hindered the investigation.
"Unfortunately, in this case, law enforcement has not received total cooperation from all families and close friends," Breault said. "It's important to note that a majority of the family has cooperated 100 percent. We feel there's someone out there that has pertinent information about the girls' whereabouts, and we'd like to take this opportunity to ask them to come forward."
A judge on Thursday granted a prosecution request to place Morrissey in a pretrial supervision program of the Iowa Department of Corrections while he faces September trials in two separate drug cases that could land him in prison for decades.
The change means Morrissey, who has been free on bond, will be supervised by parole officers who will make sure he shows up in court and does not violate the terms of his release.
Morrissey's wife, Misty Cook-Morrissey, 34, pleaded guilty in 2003 in federal court to conspiracy to manufacture and distribute methamphetamine, court documents show. She also has theft and alcohol violations in state court and is on supervised release after her probation was revoked in September because of drug and excessive alcohol use and failure to comply with drug tests.
In nearby Waterloo on Saturday, about 165 people participated in a 3-mile run/walk to benefit the girls' families, the Waterloo Courier reported. The Collinses, who have kept a low profile during the last week, were in attendance.