Now, the Indiana State Police say a man caught on camera in the area is considered a suspect.
Their bodies were found on Tuesday in a creek on private property about a mile from where they were last seen.
Police say the case is the first double homicide investigation in Carroll County's recent history.
Their families alerted the local sheriff's office when they did not return from their hike on Monday (13 February), with Abigail's mother posting a frantic message on social media when her daughter did not return, News.com reported.
Officials have declined to release the girls' cause or manner of death. Sgt. Slocum added, "We're officially calling him a suspect versus a subject we're looking to speak to".
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Investigators are urging the public to contact police with tips about the man.If you know anything about the man seen in that photo you can call and of the numbers listed. "He's going to be our main suspect at this time".
The photograph was distributed by Indiana State Police last week and appears to show a white male, dressed in a jacket and blue jeans, walking on the Delphi Historic Trail. "It's the totality of the evidence we've been developing so far that leads us to that".
"The people of Delphi are being very helpful", the spokesman said.
On Saturday, thousands gathered for a memorial motorcycle ride to raise money for the girls' families.
Indiana State Police are looking beyond the town of Delphi for a man photographed near the trail February 13 around the time a relative dropped the girls off, Sgt. Kim Riley told WLFI-TV in Lafayette.