Authorities over the weekend published CCTV images of Abedi on the night of the attack, which show him wearing a hat, glasses and a dark top. Did you see him?
"There remain a number of things that concern us about his behaviour prior to the attack and those of his associates which we need to get to the bottom of", he said.
British police made another arrest and stormed another house Sunday as they hunted for suspects in the Manchester bombing, while a government minister said members of attacker Salman Abedi's network may still be at large. The suitcase is "a different item" from what was used to carry out the bombing, Jackson said - but he added that people should be cautious and contact police if they can help track it down.
Although detectives have no reason to believe the luggage contains anything unsafe, they are warning the public not to approach it and instead call 999 immediately. Police have been searching landfills and have appealed for the public to alert them if the luggage is seen around the city.
It is highly unusual for British authorities to publicly confirm the existence of internal investigations into possible security lapses, but the British home secretary, Amber Rudd, welcomed the MI5 review Monday, saying it was "the right first step" in learning from the Manchester attack.
The Bank Holiday raids followed a flurry of police activity in Manchester over the weekend, with the arrest of a 25-year-old man in Old Trafford and a 19-year-old man in Gorton.
Severe thunderstorm watch until 9 PM
The front will produce scattered thunderstorms during the hottest time of the afternoon, daytime highs will reach the middle 90s. Several communities in west-central Alberta are being told to brace for "dangerous" thunderstorms on Wednesday afternoon.
Salman Abedi bought most of the key component parts of the suicide bomb he detonated in the Manchester Arena terror attack, police said.
A total of 16 people have been arrested in connection with last Monday's attack.
Britain's Security Service MI5 has launched two urgent investigations in order to understand how the security agencies within the country missed the warnings indicating that the Manchester Arena terrorist was planning an attack.
In the Libyan capital Tripoli, Abedi's younger brother 20-year-old Hashem and their father, Ramadan, are being held by special forces linked to the country's interior ministry.
Prime Minister Theresa May said developments in the investigation into the bombing meant that intelligence experts had chose to lower the threat level from its highest rating "critical", meaning an attack could be imminent, to "severe".
They say he returned to Britain from Libya on May 18, and likely completed assembling his bomb at a rented apartment in central Manchester.