The Manchester bomber may have built a second device, which could be in the clutches of other extremists, police have said.
Anti-terror officers made the terrifying discovery when they raided the home of Salman Abedi , after he killed 22 people in a sickening attack on Manchester Arena.
Police say they discovered a ‘working bomb factory,’ with a stash of chemicals and components that could be used to make another bomb, sources said.
Security sources believe this shows Abedi made the bomb that he used to blow himself up at the Ariana Grande gig on Monday.
A security source told the Telegraph: “The worry is there was enough to build two or three bombs and we can’t rule that out.”
Police investigating whether Abedi acted alone have raided homes across Manchester, carrying out a controlled explosion at one property.
Detectives believe Abedi was by himself when he set off his improvised explosive device at the concert on Monday night, but need to know if he had help making his bomb or planning the atrocity.
The UK’s terror threat level has been raised from ‘severe’ to ‘critical’, meaning an attack is possibly imminenet.
Soldiers have been placed on duty at vulnerable locations including Buckingham Palace, Downing Street and the Palace of Westminster.
Prime Minister Theresa May said: “The police and security services needed to investigate whether or not Abedi was acting alone.
“Those investigations continue. But the work undertaken throughout the day has revealed that it is a possibility we cannot ignore that there is a wider group of individuals linked to this attack.”
It emerged Abedi had visited Dusseldorf, described as Germany’s hotbed of radical extremism, four days before his murderous slaughter.
There have been eight arrests in connection with the case, including members of Abedi’s family.
Properties across the country have also been raided.
Greater Manchester Police has established the identities of the 22 people who died in the terrorist atrocity and specialist officers are supporting their families, but forensic post-mortem exams could take another four to five days.
The victims of the attack include a hero aunt who shielded her niece from the blast, a teenage Ariana Grande superfan, two mums waiting to pick up their children and an eight-year-old schoolgirl. ISIS has claimed responsibility for the slaughter.