A police operation that lasted five hours in Brussels' city centre on Wednesday turned out to be a false alarm, according to local media reports.
The man was wearing a heavy winter coat with protruding wires in a temperature of nearly 30 degrees Celsius, the report added.
After hours of intense operations, the man was found out to be a student of nuclear radiation at a university in Brussels. He was researching radiation and radioactivity in the city.
The man has been arrested and taken by the police for hearing.
The operation had resulted in the blockade of a large swathe of blocks, and the evacuation of several shops around Place de la Monnaie.
Special forces and the bomb disposal unit were also called in to assist the operation.
Earlier this year, Brussels was struck by three coordinated suicide bombings, which killed at least 32 civilians.