A disturbance involving a group of males thought to be carrying knives caused alarm for town centre shoppers.
Police are appealing for witnesses to the disorder at Kingsgate Shopping Centre, Huddersfield, at around 3.30pm yesterday (Saturday).
They said extra patrols had been launched following an incident of affray, in which nobody was injured.
A West Yorkshire Police spokesperson said: "Officers were called shortly after 3.30pm following a report of a group of males thought to be in possession of bladed items within the shopping centre."
Detective Inspector Mark Atkinson, of Kirklees CID, added: “Officers responded swiftly to the incident yesterday afternoon, which will have been understandably alarming and concerning for those present.
“We have a number of lines of inquiry underway and would very much like to hear from anyone who witnessed any part of what took place who has not yet spoken to the police, or anyone who has any information to come forward.”
Witnesses should call Kirklees CID on 101 with the reference number 13180056910 or Crimestoppers, anonymously, on 0800 555 111.