Fresh panic has struck Manchester following the evacuation of the Arndale Centre, where a man has been arrested.
Witnesses reported people running through nearby streets and shouting "run" on Tuesday morning.
Collette Nicholls, a member of staff from Superdrug, told the Manchester Evening News people were "running and screaming".
"Then we were all told by our manager to come out," she added. "We're all a bit shook up."
A spokesperson for Greater Manchester Police said a man was arrested at the Arndale Centre, adding: "This is not currently believed to be connected to last night's attack."
There were unconfirmed reports the arrest came after a suspicious package was found in the Arndale centre's food court.
A spokesperson for Greater Manchester Police told The Independent she could not immediately confirm the cause of the temporary evacuation.
A large police cordon was been set up around the centre and Market Street, which has since been lifted.
It came after a suicide bombing killed at least 22 people at Manchester Arena in the worst terror attack to hit the UK since 7/7.
Police said the perpetrator, a man believed to be acting alone, died at the scene.
A 23-year-old man has been arrested in south Manchester in connection with the attack.
Ian Hopkins, the Chief Constable of Greater Manchester Police, said investigators believe the attack was carried out by a lone suicide bomber “carrying” a homemade device.
“The priority is to establish whether he was acting alone or as part of a network,” he added.
Theresa May said security services have identified the bomber but that it was too early in the investigation to publicly release his name.
No group has yet claimed responsibility for the atrocity, which came exactly two months after the Westminster attack and four years after the murder of Fusilier Lee Rigby in Woolwich.
Central Manchester was previously targeted by the Provisional IRA, which injured more than 200 people with a truck bomb detonated outside the Arndale Centre in 1996.
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