Security forces named Tahmid Hasib Khan as a suspect in the weeks following the siege at the upmarket Dhaka cafe in July when Islamist militants killed 22 mostly foreign hostages.
Khan's family vehemently protested his innocence, saying he was in the cafe as a customer and was not connected to the five gunmen who hacked and shot to death the hostages in an attack claimed by the Islamic State group.
"He (Khan) was exempted as police had not found any evidence against him," Abu told AFP.
"However, police today filed another case against Khan of non-cooperation with the investigators," Abu added, although police were not going to seek his rearrest.
Khan, a University of Toronto student who was back in his homeland on leave, did not speak with reporters as he left court.
Khan and Hasnat Karim, a British national of Bangladeshi origin, were both inside the cafe when gunmen staged their raid on July 1, taking a group of mainly Western diners hostage.
Police had denied the men were in their custody before announcing on August 4 that they had been arrested.
Abu said today that Karim, whose family has also denied his involvement, remained in jail.
Bangladesh's national police chief has said the two had fallen under suspicion as a result of their "behaviour and actions" during the siege.
Reports in local media said Khan was seen holding a firearm and Karim strolling with the attackers on the roof.
The siege was by far the deadliest in a string of attacks claimed by Islamist groups which have blighted Bangladesh over the last three years.
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