A police helicopter was deployed after someone was reportedly seen running around a park with a knife.
Hertfordshire Constabulary says it was called to reports that a group of males were running through Verulamium Park in St Albans around 4.41pm on Monday, March 29.
One was seen holding what was believed to be a knife, police said.
Officers were immediately sent to the scene and they carried out an extensive search of the area with support from the National Police Air Service.
No one suspicious was found and there were no reported injuries.
Police are investigating the incident.
Anyone with information can call 101 quoting ISR 505 of 29 March. Information can also be reported online at herts.police.uk/report.
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