Police are continuing to question a man in connection with the shooting of Pc Sharon Beshenivsky after releasing five other people.
Pc Sharon Beshenivsky joined the Bradford South team in May
Pc Beshenivsky was shot dead and her colleague, Pc Teresa Milburn, injured during a robbery in Bradford on Friday.
Two men, both 22, an 18-year-old man and a 24-year-old man have now been released on police bail. A woman, 18, has been released without charge.
One man, 31, is still being held in police custody.
Pc Beshenivsky, 38, died after being shot in the chest on her youngest daughter's fourth birthday. She had been a serving police officer for nine months.
Her colleague Pc Milburn, 37, who joined the West Yorkshire force in April 2004, was shot in the shoulder.
Both officers had been wearing body armour which provided limited ballistic protection.
The five men and a woman were arrested in London on Saturday.
Hundreds of floral tributes to Pc Beshenivsky have been laid outside the police cordon at the scene of the shooting, a travel agency on Morley Street.
On Tuesday, the son of Pc Beshenivsky visited the site where she was shot to leave a floral tribute from him and his brother, Paul, seven, and sister Lydia, four.
Samuel, 12, laid down a bouquet with a note which read: "To Mum, Good luck. We all miss you. Love always from Samuel, Paul and Lydia."
Police chiefs have described the shooting as their "worst nightmare".
West Yorkshire's Chief Constable Colin Cramphorn said he had "searched his soul" about what could have been done to prevent Pc Beshenivsky's death and Pc Milburn's injuries.
But he concluded the officers had the right protective equipment and back-up to deal with the robbery.
He also described the heart-breaking scene when he visited Pc Beshenivsky's family in Keighley on Saturday to be confronted with the sight of her four-year-old daughter's unopened birthday presents.
"That is an image that is just seared into my brain," he said.
Pc Beshenivsky's husband Paul has described the mother-of-three children and two step-children as his rock.
"She was loved by everyone who met her and my family's loss is felt by so many.
"It breaks my heart to think that I will never hear her infectious laugh again."