The Fishers were victims of a planned attack, police believe

Graham and Carol Fisher, aged 60 and 53, were attacked at their bungalow and petrol station on the A39 near Wadebridge on 5 November

About 2,500 people were interviewed at a roadblock set up on Wednesday night close to the murder scene, one week after the murders.

Officers at Bodmin police station are using the latest computer technology to examine information that has come in from the public.

A no-fly zone has been imposed over the bungalow to preserve the crime scene.

Police also say they want to trace a hitchhiker seen on the A39 on the evening of the murders.

High morale

Senior officers say the response has been excellent, but they need the continued support of local people.

They also say morale is high and they are totally focused on their task of helping find the killers of the Fishers.

Investigation chief Detective Superintendent Stuart Newberry said the role of the incident room team is vital.

He said: "The work they do is methodical, it's time-consuming and laborious.

"But it really is essential and the people that we use are highly-trained in this and are allowed to get on with this work to make sure we don't miss any opportunities at all."

Supervising officer Sergeant Paul Stoyles said: "We have about 12 officers working directly in our incident room.

"But we also typists and disclosure officers in another room, and an exhibits officer and detectives. There are loads of them.

"The public response has been tremendous so far, but that is not to say they should stop ringing in. What they regard as insignificant may be very important to us."

Although there is some concern the longer the inquiry goes on, the less response police will get, officers still believe people will help.

Sergeant Stoyles said: "There may be a danger of less response, but this was such a horrific attack that it's going to be in the back of people's minds for a long time to come."

The hitchhiker police wish to trace is described as a man in his 30s walking in the rain, but not dressed for the conditions.

Police says it is likely he is nothing to do with the incident but they wish to talk to him to rule him out of their inquiries.