The suspects have been accused of creating panic in Turin's San Carlo square, where 30,000 people had gathered on June 3 to watch local team Juventus play Real Madrid, by shooting pepper spray into the crowd while trying to commit a robbery.
Erika Pioletti, 38, was at the square with her boyfirend and died two weeks later after being left in a coma by the crush.
Mr Pioletti's partner, Fabio Martinoli, blasted the event's organisation.
"There were unauthorised vendors everywhere, anyone could come in without any checks," he told Italian daily La Repubblica at the time.
Turin mayor Chiara Appendino was criticised for not implementing the safety measures required for such a large event, with Italian media highlighting the absence of an emergency evacuation plan.
Ms Appendino was one of those targeted in a probe for murder and criminal injury – closed on Thursday – alongside her former chief of staff Paolo Giordana and Angelo Sanna, the police commissioner in charge of public safety the night of the stampede.
That investigation could subsequently be taken to court.
AFP reporters who witnessed the stampede, which took place a few minutes before the end of the game, said the panic seemed to have been triggered by loud bangs from the fireworks, followed by people shouting that a bomb had exploded.