Police are examining the possibility that the gunman who killed bank manager Alistair Wilson on his doorstep could have escaped by boat.
Alistair Wilson, pictured on a family outing on the day he was murdered
The 30-year-old was shot in the head at his home in Nairn on Sunday evening.
Northern Constabulary have said they are looking at two separate pieces of information relating to boats at the harbour.
Officers are also looking into reports that a speedboat was found at the other side of the Moray Firth from Nairn.
Meanwhile, the BBC's Crimewatch programme has offered its assistance to detectives investigating the murder.
Five days after Mr Wilson was shot dead, police are no closer to finding his killer or a motive for the shooting.
Detective Chief Inspector Peter MacPhee, the man leading the inquiry, said there was
"clearly much work still to be done" and officers were continuing to sift through the information which had come in.
He added: "I have always been of the opinion that I would consider all options available to me and that includes the possibility of dealing with Crimewatch.
"The benefit of such a programme is of course the national aspect."
The door where Alistair Wilson was shot dead
In an effort to gather more information, about 30 officers will be stopping vehicles and people in Nairn on Sunday and asking them what they were doing on the night of the murder.
Signs will also be put up in the town asking people to contact police if they believe they know something which could help the inquiry.
Mr Wilson's wife, Veronica, opened the door to the killer, who asked for her husband by name.
After the shots were fired the gunman ran from Crescent Road towards the links area of Nairn.
Mr Wilson, the father of two young boys, was rushed to hospital where he died.
The gunman is described as being aged 35-40, stocky, clean shaven and wearing a baseball hat and blouson jacket.