Detectives said today they were "actively seeking" three men in connection with the murder of Pc Sharon Beshenivsky.
West Yorkshire Police made the announcement as a 31-year-old man was released on bail pending further inquiries.
He was the last of six people arrested in London over the weekend to be released from custody in connection with the death 38-year-old Pc Beshenivsky and the shooting of her colleague Pc Teresa Milburn.
A spokeswoman for West Yorkshire Police said: "Following significant developments in the investigation over a short period of time, West Yorkshire Police are now actively seeking three men who we wish to question regarding the events in Bradford on Friday."
The six people arrested in London on Saturday - the day after the shooting of the two officers outside a travel agent's in Morley Street, Bradford - were brought to West Yorkshire in a dramatic armed convoy but they have now all been released.
The five men, aged between 18 and 31, have been released on bail pending further inquiries. An 18-year-old woman was released without charge.
Senior officers also revealed today they are seeking information about a four-wheel-drive car they have recovered.
Detective Superintendent Andy Brennan, who is leading the inquiry, said: "Detectives from West Yorkshire Police's homicide and major inquiry team have been in London since Saturday and continue to work closely with our colleagues in the Metropolitan Police.
"We are now appealing for information about a silver Toyota Rav 4 motor vehicle, registration number WP05 YTT.
"The vehicle was hired at Heathrow Airport on October 25 2005.
"We believe the vehicle travelled to West Yorkshire from London in the early hours of Friday November 18 and returned to London later that evening.
"We are appealing for anyone who has seen this vehicle at any time in West Yorkshire but particularly on Friday November 18, and anyone with information as to the occupants of the vehicle on that date, to contact us.
"The vehicle is now in police possession.
"West Yorkshire Police has received an extremely good response from the community to the tragic events of Friday and we are grateful for that.
"Witnesses are still coming forward and we would urge anybody else who may have been in Morley Street, or who has any information and has not yet contacted us, to do so."Reuse content