The 26-year-old man arrested in connection with the suspicious package incidents in Piccadilly Gardens and at Oldham Library has been sectioned under the Mental Health Act 1983.
The investigation into the full circumstances surrounding the incident on Friday, May 3 remains ongoing.
Two packages in Piccadilly Gardens were examined by officers with support from bomb disposal officers on Friday afternoon.
Around 6.15pm, loud noises were heard after one of the packages was made safe.
Earlier in the day, Oldham Library was evacuated after reports of a suspicious device found there.
The library remained closed on Saturday, May 4 to enable police to complete investigations and Oldham Council said: “We apologise for any inconvenience caused and hope to reopen as normal next Tuesday following the Bank Holiday weekend.”
All three packages have been deemed non-viable but cordons remained in place at both locations while enquiries are carried out.
The 26-year-od man was arrested on suspicion of a bomb hoax offence, possession of a prohibited weapon, possession of a bladed article and possession of an offensive weapon.
Police Superintendent Dave Pester of GMP’s City of Manchester Division, said: “I know today’s events have caused a lot of disruption to people, businesses and transport but I cannot thank everyone enough for their patience as we’ve responded to this.
“The investigation will look at every available piece of information so we can understand the motivation behind it and the circumstances that surround it.
“People’s safety is always our priority in everything that we do, which is why we have taken this extremely seriously and responded the way that we have.
“I’d like to once again thank you for your patience as we progress our enquiries and assure you that any updates we have on the investigation will be shared with you.”