Rejecting reports the bomber had recently returned to Britain from Libya, Mr Abedi said his son Salman had visited Libya more than a month ago. Speaking from Tripoli, Mr Abedi told the Associated Press: "We don't believe in killing innocents. This is not us." Mr Abedi confirmed his son Ismail, who was born in Westminster in 1993, was arrested on Tuesday.

The Special Deterrence Force in Libya is under the Department of Interior. Here is their Facebook page and the announcement of Hassam Abedi's arrest (there's a translate feature.) It says he confessed. Who wouldn't after being arrested by them? Text of their statement (translated by Facebook) below:

The Special Deterrent Force has been able to arrest one of the suspects with the authority of the state of ISIS, which lasted for almost a month and a half until the information received from the investigation teams was up to act as a terrorist act in the capital city of Tripoli.

The Information was presented to Mr. Head of the investigations section of the attorney general's office, which ordered the suspect to be arrested as soon as possible, and on 23-5-2017, he was arrested approximately 23-5-2017 p.m.
The arrest was promptly received during the receipt of an estimated $ 4500 million. To be funded by guy,.

After the initial interrogation, he said:

Hashim Ramadan Abu Al-Qasim Al-denominator

Born in 8.4.1997 in Manchester English.
University student in Manchester UK
He also reported that he was a member of the state of ISIS with his brother / Salman Al-Labidi and admitted to his presence in Britain during the preparation period and found out he was fully aware of the details of this terrorist operation
It's worth mentioning that he came out of Britain on 16.4.2017th and admitted that he was on constant contact with his sister.</