Officers nationwide have offered cover to colleagues in Greater Manchester Police so they can attend the funerals of the two killed PCs.
Manchester's police chief said he expected "developments" in the next 24 hours over possible charges relating to the deaths of two officers.
Over 50,000 tributes have been posted to Greater Manchester Police's online book of condolence to the two killed officers and Facebook page.
The parents of PC Fiona Bone, who was killed alongside her colleague PC Nicola Hughes on Tuesday, said they felt "numb" when they heard the news and described their daughter as "calm, collected and hugely adventurous" who "always wanted to go where the action was".
Speaking to the Manchester Evening News, Paul Bone and his wife, June, admitted that they had not slept at all since the death of their daughter.
"We’re shocked, just numb," Mr Bone said.
He added: "We heard on the news that two police officers had been shot and within three minutes two policemen were at the door. That’s when we heard – at 1.03pm."
"She was calm and collected, nice to be around. We will miss her so much."
Pc Fiona Bone has been described as "a wonderful daughter, sister, partner and parent."
She had been planning a civil partnership with her partner Clare before she died.
The family of PC Nicola Hughes has released a statement saying: "Nicola always wanted to make a difference and, in doing so, she made such a big difference to everyone she knew.
"She cared about everyone and especially her colleagues.
"Nicola was only 23 years old and had the whole of her life in front of her.
"We cannot express how we feel today except to say we have always been exceedingly proud of Nicola and always will be.
"She knew she was loved by us all and we shall all miss her dreadfully."
Home Secretary Theresa May, who had cut short her holiday to return to Greater Manchester Police, has described the murder of two police officers as "savage acts of pure brutality."
The Manchester United team have worn black armbands in a mark of respect for two police officers gunned down in the city yesterday during the UEFA Champions League at Old Trafford against Galatasary.
Sir Peter Fahy today said that the Greater Manchester Police were still searching for more grenades after the gun and grenade attack which killed two police officers.
He said: "We are not confident that we have recovered all the grenades. We don't know for certain, we've made it clear to our officers that the threat is still there."
Greater Manchester Police have said that one of the officers' Tasers was found on the ground out of its holster at the scene where two unarmed police officers were shot yesterday.
Sir Peter Fahy has defended the decision to release Dale Cregan on bail and said that "in the normal course of complex inquiries, there is not enough evidence to justify a charge and therefore that person has to be released."