Samuel Babin, a student at the Blekinge Institute of Technology, was last seen January 11 in a laundry room, Sweden's The Local.se reported Wednesday.
Blekinge County police said they haven't been able to trace Babin's mobile phone and no withdrawals have been made from his bank account.
Authorities now believe foul play may be involved in his disappearance and a kidnapping investigation has been launched.
Tuesday, Missing People Sweden and police went to Dragso Island on the outskirts of Karlskrona, a camping and recreation area Babin was fond of.
A search of the island's woods and beaches failed to turn up any trace of the missing student, police said.