A 17-year-old boy was arrested following a stop search on a vehicle in Horsemarket this week.
The incident happened when Northamptonshire Police carried out a stop on a vehicle, near Roadmender, at about 1.30pm on Monday, December 31.
A spokeswoman for the force today (Wednesday) said: "A number of items were recovered and four people were arrested on suspicion of possession of an offensive weapon.
"Three have been released with no further action and a 17-year-old boy has been released under investigation while enquiries are ongoing.”
An eyewitness told the Chronicle & Echo that he saw sniffer dogs and armed police outside the live music venue on the day.