Officers investigating an alleged incident in Watford are appealing for information and witnesses.
It happened on Market Street, near to Mangans, at 9.25pm on Friday, 14 June.
It was reported that a man became involved in an altercation in the street and subsequently threatened other people with a knife. No one was injured.
Officers immediately attended and detained a man on nearby Percy Road before recovering a kitchen knife from a litter bin.
Detective Inspector Jason Finnegan, from the Watford Local Crime Unit, said: “We are conducting a number of lines of enquiry at this time however we would be keen to speak to any witnesses who saw what happened and have not yet spoken to us.
“You may have vital information that could assist our investigation so I am urging you to come forward.”
You can report information online or speak to an operator in our Force Communications Room via web chat here, quoting reference 41/53780/19.
You can also call the non-emergency number 101, and ask for Herts Police.
Alternatively, you can stay 100 per cent anonymous by contacting the independent charity Crimestoppers on 0800 555 111 or via their untraceable online form.