The man said he had found the bag outside his apartment and had thought it was intended as a threat against him. He claims he took the bag to the train, and left it there when he got off. The train and bus stations in Södertälje were sealed off while the bag was examined by explosives experts.
It was later revealed that the bag contained 125 grams of dynamite. Police say that the bomb could have caused damage up to 300 metres away.
The man is now being questioned, and police say he was recently released from a long prison sentence. They say they believe his story.
“He has been able to give a description of the contents of the bag, and has described events in a way that we judge to be credible,” said Ulf Göranzon, press spokesman for Stockholm Police, to TT.
Göranzon would not give details of why the man left the bag on the train, but said that police were satisfied with his explanation.
Police had earlier suspected there to be a link between the explosives and a nearby meeting of the extreme-right National Democrats. The man currently under arrest claims he has no link to extreme right-wing or left-wing groups.
The man is now under suspicion of negligence constituting a public danger, Göranzon confirmed. If found guilty, he could face prison.