Three men are now in custody in connection with the murder of Corporal Melvin Smith on the weekend.
The 38- year old policeman was shot dead at about 8 p.m. on Manchester Road, Manchester while helping a citizen who was being robbed of his motorcycle.
Head of Police Area Three, Assistant Commissioner Clifford Chambers, says the men were arrested on Saturday night.
ACP Chambers says the men are to face an identification parade this week. He says the police should close their investigation into the matter soon.
Corporal Smith was assigned to the Manchester Community Safety and Security Branch.
Police Commissioner, George Quallo and Commissioner of the Independent Commission Investigations, INDECOM, Terrence Williams, have condemned the killing.