Samuel Babin was last seen on January 11th and was reported missing by fellow students at the Blekinge Institute of Technology.
"There's nothing to indicate he disappeared voluntarily," Lotta Hansson, spokeswoman with the Blekinge County Police, told the Expressen newspaper.
Police now believe foul play may be involved in Babin's disappearance and on Tuesday launched a preliminary kidnapping investigation.
Babin was last seen in a laundry room, and since his disappearance police haven't been able to trace his mobile phone. Nor have any withdrawals been made from his bank account.
According to a description published on the Facebook page of Missing People Sweden, which has been involved in the search for Babin, he has blue eyes, long, light brown hair, and sometimes wears glasses.
He is about 175 centimetres tall, weighs between 75 and 80 kilogrammes and is believed to be wearing blue jeans and black sneakers.
On Tuesday, Missing People and police worked together to search for Babin at the Dragsö island camping and recreation area on the outskirts of Karlskrona.
According to fellow students, Babin was fond of the island, but a search of the island's woods and beaches failed to turn up any trace of the missing French student, leading police to launch a probe into his possible abduction.
If no progress is made in the case, Missing People plans to organize a more extensive search party on Saturday.
Anyone with any information about Babin or his possible whereabouts is encouraged to contact Swedish police at 114 14.