Plans for a UK trial of the brother of the Manchester Arena suicide bomber are under way as extradition proceedings remain ongoing.
Hashem Abedi is currently in custody in Libya. An extradition application was made six months ago.
The head of the North West Counter Terrorism Unit, Assistant Chief Constable Russ Jackson of Greater Manchester Police, said a team of about 100 investigators continue to work full-time on the live murder investigation
Both brothers travelled to Libya in April 2017.
Salman returned alone before carrying out the terror attack on May 22 - which left 22 dead and hundreds injured.
Hashem Abedi, 21, is understood to be currently held by a militia group in Libya.
A warrant for his arrest in relation to questioning over allegations of murder, attempted murder and conspiracy to cause an explosion was also issued before the extradition request was handed to Libya on November 1 last year.
Mr Jackson added that it was "really difficult" to provide any further detail of the extradition process.
He said: "Firstly we must respect the Libyan legal process and we are very grateful to them for considering our request.
"Secondly, it is vital that the court process is respected in this country and especially the right to a fair trial.
"It is because of this that we cannot comment on any specific detail of the case.
"When we can say more, we will of course do so.
Mr Jackson said they had now established that more than 800 people suffered physical and psychological injuries from the bombing.
He said: "Over the past year the investigation team has worked hard to support those affected and we are consistently moved by the grace and dignity they show in trying to repair their lives.
"Of course for many the loss is too great for them to ever make a full recovery from this terrible event."
Police have previously said they do not think Salman Abedi was part of a wider network but believe others were involved in the planning of the attack and named Hashem as a suspect.
The Abedi family, originally from Libya, fled during the Gaddafi dictatorship with his father returning to fight with opposition forces when the uprising began in 2011.
An extradition agreement between the UK and Libya had been agreed in 2009 but since the overthrow of Gaddafi the country has been split into warring factions with the United Nations-backed, internationally recognised Government of National Accord (GNA) struggling to assert control over swathes of the country in the hands of dozens of different militias including Isis-affiliated groups.