Story highlights Police release photo of Manchester bomber with a large suitcase

Home Secretary says it's right for British security agency to investigate itself

London (CNN) Hours before he set off a bomb believed to be hidden in a backpack, Manchester Arena suicide attacker Salman Abedi walked city streets toting a bright blue suitcase.

Greater Manchester Police on Monday released two photos and asked for the public's help in their investigation of the May 22 attack that killed 22 after an Ariana Grande concert.

"Did you see Abedi with this suitcase between the 18 and 22 May 2017?" Detective Chief Superintendent Russ Jackson asked in a statement. "Where did you see him with it during that time?"

This image of Salman Abedi with a suitcase was taken on the day of the concert attack.

"We have no reason to believe the case and its contents contain anything dangerous, but would ask people to be cautious," said Jackson.

Police said the attacker had the suitcase in at least two Manchester neighborhoods.

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