Officers remain under threat after the deaths of two policewomen in a grenade and gun attack, the Chief Constable of Greater Manchester Police has warned.
Sir Peter Fahy said he could not be sure all the explosive devices had been recovered from the area where Pcs Nicola Hughes and Fiona Bone were attacked.
Two men have been arrested and are being questioned over their deaths - Dale Cregan, 29, who was one of the country's most wanted men, and a 28-year-old.
The second man was detained in the Hattersley area on suspicion of conspiracy to murder, Sir Peter said.
Cregan, who was wanted for questioning over the deaths of father and son David and Mark Short, handed himself over to police shortly after the two officers were killed.
It is understood that a desk officer kept him talking while an armed unit was scrambled to the scene, and he was arrested.
Speaking to reporters, Sir Peter said: "We are not confident that we have recovered all the grenades, we don't know for certain, so we've made it clear to our officers that the threat is still there.
"I would want that to be the message, this has been a long-standing criminal feud between different outfits in Manchester and in the Tameside area, and that threat is very much there."
He said that the force had issued Osman warnings - notices given to people under threat of being murdered or seriously injured - to "a large number of individuals".
Sir Peter had suggested that the two officers were lured to their deaths, telling a press conference that a call had been made reporting a burglary at the address. The force added that one of the officers' Tasers was found on the ground out of its holster at the scene.