Police officers seized 40 knives after stopping and searching people in Rotherham over a three-month period.
Officers used a knife arch as part of Operation Alligator – an initiative launched earlier this year to tackle anti-social behaviour, knife crime and violence across the town.
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Since September, 40 blades have been seized but South Yorkshire Police said there has been a slight increase in knife related crimes.
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Sergeant Simon Kirkham, who is in charge of Operation Alligator, said: “We do not wish to cause undue alarm, as being a victim of such crime is rare but we do thank our communities for their support and understanding.
"Clearly we would always prefer to prevent but those that persist and carry a knife in a public place can expect robust action and if it’s a second occasion we find you committing this offence a mandatory minimum of six months imprisonment will apply but can be up to four years.
“Do not carry knives. If you are a parent or guardian, take every opportunity to dissuade your young people from obtaining them and carrying in them.
“All that said, the vast majority of Rotherham residents are law abiding and it is relatively unlikely you will be a victim. We appreciate your support.”