The man, who is said to have grown up in the southern city of Malmö, was identified from closed circuit video as an accomplice of Khalid el-Bakraoui, the Belgian national who blew himself up at the Maelbeek station on March 22.
On Saturday, Belgian authorities confirmed to Swedish Radio that the man is suspected of being involved in the attack and prosecutors claim the suspect also bought the bags used for the suicide bombs.
Swedish Radio reported that Belgian police were still interviewing the man on Monday afternoon.
Swedish Radio's local channel in Malmö reports that local imam Ali Ibrahim knew the man and his family, who were shocked by his decision to travel to Syria to fight with the Islamic State.
Pictures posted on the man's Facebook page in early 2015 show him wearing a camouflaged shirt and hoisting an assault rifle with an Islamic State flag in the background.
Swedish terrorism expert Magnus Ranstorp told Swedish Radio that he wasn't surprised by the link between Malmö and the attacks in Brussels.
Ranstorp co-authored a 2009 report warning about the spread of Islamic extremism in the Rosengård neighborhood of Malmö, the same area where the suspect grew up, according to Ibrahim.
The report called for closer cooperation between the state and local municipalities to help stamp out radicalization before it became too serious.
"But," Ranstorp told Swedish Radio, "it's seven years too late."