A youth club being held at Blackwood Comprehensive School was tonight placed in lockdown following reports of a knifeman on the loose.
Police later found a man matching the description without a knife and believe the erroneous report was made in good faith.
Armed police, a dog unit and police helicopter all attended the incident, which lasted for an hour and 45 minutes.
In a statement, Gwent Police said: “At around 8pm this evening, Wednesday March 6, we received reports that a man had been seen in the grounds of Blackwood Comprehensive School, close to the Cefn Road area, with a knife.
“Specialist officers attended including firearms, dog section and police helicopter and a search was carried out of the surrounding area.
“Officers located and spoke to a person matching the description of the man, however following further investigations, it transpired that the male was in possession of a mobile phone which appears to have been mistaken for a knife.
“Officers are treating this as a report made in good faith and we are no longer treating this as a suspicious incident.”
Police confirmed the incident ended at around 9.45pm with the children allowed to leave.