Several schools in Lake and Porter counties went into lockdown after the threats.
They included schools in Hobart, Portage and Valparaiso.
The threats were made throughout the month of January.
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Investigators determined the threat was not credible.
No further information about the teen taken into custody was immediately available.
"We understand the anxiety a situation like this can cause. Many of us here at PPD are parents as well and have children attending Portage Township Schools," Portage police said in a statement.
Valparaiso police also thanked the United States Secret Service - Chicago Field Office, United States Secret Service - Forensic Services Division in Washington D.C. and Federal Bureau of Investigations - Indianapolis Field Division, among others, in the investigation.