A man has been arrested on suspicion of assisting the Manchester Arena bomber ahead of the 2017 attack that left 22 victims dead.
The 24-year-old suspect was detained at Manchester Airport on Friday, shortly after arriving in the UK.
Greater Manchester Police said he was arrested on suspicion of engaging in the preparation of acts of terrorism, or assisting others in acts of preparation.
The suspect is originally from the Fallowfield area of Manchester, but had left the UK in 2017. He remains in custody for questioning.
Simon Barraclough, the senior investigating officer in the ongoing Manchester bombing investigation, said: “Greater Manchester Police remains firmly committed to establishing the truth surrounding the circumstances of the terror attack at the Manchester Arena - whether that is by supporting the ongoing public inquiry or by continuing to pursue leads with regards to the criminal investigation.
”Over four years have passed since the atrocity took place but we are unwavering in our dedication to follow each line of enquiry available so that we can provide all those affected by the events at the arena with the answers they rightly deserve.”
He was handed a life sentence for murder last year, after prosecutors said he was “just as responsible” for the deaths of the victims as his suicide bomber brother.
The man arrested in Friday is understood not to be the plotters’ older brother Ismail Abedi, who fled the UK before he was due to give evidence to an inquiry into the attack.
Several associates of Abedi were questioned by police following the bombing, which was claimed by Isis, but none were charged with offences at the time.
The bomber had been linked to a network of Isis supporters in Manchester, including a man convicted for helping jihadis travel to join the terrorist group in Syria, and was previously investigated by MI5.
An ongoing public inquiry is working to establish how Abedi was radicalised, and whether there were any security failures in the lead-up to the bombing or issues with the emergency response.