Police in Offenbach, next to Frankfurt, told the dpa news agency on Wednesday that the suspect was a 48-year-old resident with Serbian citizenship. Further details were to be released Thursday.
Markus Wuerth, the son of the Wuerth tool and hardware company chairman Reinhold Wuerth, was abducted in 2015 in an area northeast of Frankfurt.
The victim, who was 50 at the time, was found a day later about 100 kilometers (60 miles) southeast of where he was seized.
The kidnapping prompted a police manhunt, which authorities speculated may have prompted Wuerth's release, and a multi-million euro ransom was demanded but not paid.
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