Armed police staged a raid at a housing estate weeks before two officers were targeted at an address there in a fatal gun and grenade attack, sources have confirmed.
A search took place on the morning of August 16 at a house on the Hattersley estate in Greater Manchester as part of the investigation to trace wanted murder suspect Dale Cregan.
Pc Nicola Hughes, 23, and Pc Fiona Bone, 32, were killed at a different address on the estate on Tuesday when they responded to a report of a burglary in the area.
Cregan has been charged with the murders of Pcs Hughes and Bone, two more counts of murder and four of attempted murder.
It is understood that no arrest was made in relation to the August 16 search. No-one from Greater Manchester Police has commented on that raid.
In the immediate aftermath of the deaths of Pc Hughes and Pc Bone, Chief Constable of Greater Manchester Police Sir Peter Fahy said the house in Abbey Gardens where the officers were called to was not known to them.
"It has not featured in this particularly huge inquiry we have undertaken. So it would be routine to have unarmed officers sent to the scene," he said.
The investigation into the murders of father and son David and Mark Short, which Cregan is also accused of, involved officers on armed patrol 24 hours a day, seven days a week, in the Clayton and Droylsden areas, he added.
But he explained that "clearly we cannot send armed officers to the hundreds of incidents we get not only in these areas but also in other areas". He said: "These were two officers going about their normal duties. Like all officers, they went to a variety of incidents not knowing what it was that they would face."
Police have been given more time to question a 28-year-old man arrested on suspicion of conspiracy to commit murder in relation to the deaths of Pc Bone and Pc Hughes. This is due to expire at 9.15am on Saturday, Greater Manchester Police said.