A terror alert was sparked after a replica suicide vest was discovered in Sheffield city centre.
Specialist officers were called out to Furnival Gate after a member of public reported that an item hung on railings resembled a suicide vest.
Police checked the item and it was found to be a homemade replica. The vest contained no viable parts or explosive elements.
Following the hoax incident, at 12.11pm on Thursday, November 19, South Yorkshire Police are now warning against the dangers of terrorism related pranks.
Detective chief inspector Steve Whittaker, from the Sheffield Local Policing Unit, said: “While the item was quickly determined to be a hoax, given the recent events in Paris, this clearly had the potential to cause widespread distress and draw a significant policing response.
“Following investigation, I believe this incident was an ill-judged prank, but people must remember the very real dangers of this type of behaviour.
“If someone had been seen with the vest the policing response would have, in all probability, involved armed officers and placed the individual in very serious danger.
“Recent events in Paris have brought into sharp focus the type and scale of threat posed by international terrorism, and the relationship between the police and the public needs to be stronger than ever before to counter this threat.”
He added: “The member of the public did exactly the right thing in contacting police immediately, but it’s vitally important that policing resources are used to deal with real threats and not foolish pranks.
“People are asked to remain vigilant, and to report anything that could be terrorist-related to specialist officers via the confidential Anti-Terrorist Hotline on: 0800 789 321.
“An investigation is ongoing to establish who left the item and I would ask anyone with information to come forward.”
Anyone who can assist the investigation is asked to contact police via: 101 and quoting incident number 454 from the 19 November.