Cambridgeshire Police are treated the deaths of three men found in the Peterborough area as murder.
Kevin Lee, 48, was found stabbed to death on Easter Saturday in the Newborough area. The bodies of two men, one in his 30s and the other in his 50s, were found at Thorney Dyke on Wednesday.
Detectives are now linking the killings and have launched Operation Darcy to investigative all three murders.
Five people have been arrested in connection with the inquiry.
Cambridgeshire Police have drafted extra officers into the inquiry.
Detective Superintendent Jeff Hill said: "This inquiry is a priority for the force and we have a large team of detectives working on it.
"There will also be extra police officers out on patrol in the areas where the bodies were discovered.
The bodies of the two men were discovered at Thorney Dyke near Peterborough by a member of the public on Wednesday morning. The area remains cordoned off.
Formal identification of the men has yet to take place and the cause of death will be determined at a post mortem examination at Peterborough hospital on Friday.
Me Lee was last seen at 2pm on Good Friday and was reported missing later that day. Hi body was discovered in a ditch on Easter Saturday.
A 36-year-old man, who was charged with perverting the course of justice, appeared at Peterborough Magistrates' Court on Wednesday and has been remanded to appear at Peterborough Crown Court on April 10.
A 47-year-old man and the 30-year-old woman who were arrested in Hereford both remain in custody.
A 32-year-old man and a 23-year-old man arrested in connection with the murder over the weekend have been released on bail.