The attempted abduction of a serviceman outside an RAF base was "quite possibly unrelated to terrorism" and may have been a road rage or robbery incident, a detective has said.
The married airman in his late twenties was out running in the village of Marham, in Norfolk, at around 3.10pm on July 20 when he was ambushed by two men.
The victim said he was near RAF Marham when he was grabbed by a man who tried to drag him towards a nearby car.
He told police he knocked the first attacker to the ground and an accomplice, carrying a knife, helped him up before both men fled.
Norfolk Police said an investigation had cost around £71,000 to date, officers had analysed more than 500 calls from the public and hours of CCTV footage and a dozen officers remained "dedicated to this investigation".
Detective Superintendent Paul Durham, from the Norfolk and Suffolk Major Investigation Team (MIT), said: "The work the team has carried out over the last five months has been very productive - particularly in identifying the most important drivers of the vehicles seen in the CCTV footage we released.
"While I continue to maintain an open mind, the inquiries completed so far lead me to believe that the motive for this attack is quite possibly unrelated to terrorism.
"While it is very easy to understand how the incident could be perceived as being terrorist-related - particularly from the victim's perspective - there are good reasons to believe that there is another explanation for it.
"What has been established through the painstaking CCTV work is that something definitely happened to the victim while he was out on his run in the area where he reported being attacked.
"Our primary task is to establish what exactly the motivation for that was and we are revisiting the possible motives of robbery, road rage to name two.
"Certainly, I am becoming increasingly persuaded that the solution to this mystery will be found locally."
He said he remained confident the case would be solved.