Keller, 18, of Plainfield, Ill., was last seen in Prairie Park near the DeKalb campus of Northern Illinois University on October 14. Burnt human remains found near items belonging to Keller are believed to be that of the missing freshman-- although a positive identification has not been made due to the condition of those remains.
The person of interest is being held on charges of obstruction of justice and unlawful possession of a motor vehicle. Extradition is pending. Officials did not release details about the arrest.
DeKalb Police Chief Bill Feithen said the investigation continues.
"I want to thank the public for the numerous tips and leads they have provided in this case," Chief Feithen said in a statement. "We are especially interested in any information about suspicious subjects and activities, especially fires, in Prairie Park between midday October 14th and the morning of October 18th."
Those with information should call 815-748-8407, 815-753-8477 or Crimestoppers at 815-895-3272.
Chief Feithen said officials have followed up more than 200 leads in the case.
Mary Tarling, Keller's cousin and the spokesperson for her parents, reacted to the latest development Thursday night.
"It's good news but at the same time it's making it more tangible that there's a human being there that did this. And that's reprehensible," said Tarling. "Whoever these 210 people are that provided these tips, we're grateful someone who doesn't have to would step forward and take even if it you think, did I see something?"
At NIU, students have been anxious and on edge. The news that someone is in custody is providing some relief.
"There is a big sigh of relief. We are uncertain but the best thing is that the police are at work now and campus feels that sense of relief," said Arielle Kalvelage, NIU student.