All four had been placed in pre-trial detention last week on suspicion of murder and attempted murder with terrorist intent but two of them were later cleared, a statement from the National Bureau of Investigation (NBI) said.
"There is no longer any reason to suspect them of these offences," it said.
Of the two left in custody, one is the main suspect -- 22-year-old Abderrahman Bouanane, a Moroccan national who was shot in the thigh by police minutes after the attack.
Three of them were released on Saturday.
Police have said Bouanane targeted women during his rampage through Turlu's market square, killing two women and wounding another six, as well as two men who tried to stop him.
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