A running club sparked a major alert when it scattered flour to mark the route of a fun run through a Norfolk town.
Police and firefighters sealed off part of the Tuesday Market Place, in King's Lynn, on Saturday afternoon after a man was seen leaving piles of an unknown white powder on the pavement.
An environmental protection unit was called in the analyse the substance. Firefighters said it was harmless corn starch after checking samples.
Police later issued descriptions of a man and woman they wanted to speak to after the incident.
Today it emerged the piles of flour were left to mark the route of a run by the Norfolk Hash House Harriers, which was hosting 40 visiting runners from Bicester, near Oxford.
'It's a harmless social activity,' said organiser Bob Green, from Oxford. 'The biggest problem in this era of social media and after Salisbury, the general public is much more aware of substances in the streets.
'As hashers, we maybe need to communicate better with the police to avoid them sending out hazardous chemicals or other expensive emergency services.'
Mr Green said he called police to inform them the flour was harmless and why it had been placed around town as soon as he heard the Tuesday Market Place had been cordoned off.
The harriers describe themselves as a social group, which meets at a different pub for a run each week.
This week's destination was the Stuart House Hotel, in Lynn's Goodwin's Road.
Flour was left in a number of locations including The Walks, the market place and South Quay to mark the five-mile route.
The trail was laid by Dave Armes, landlord at the hotel, who has been taking part in hash runs since the 1980s. He said: 'We all apologise for any inconvenience caused.
'That was completely over the top, it was a lot of fuss about nothing but for those people who didn't know what it was it was understandable.
'I think it was really good that the public was being vigilant and reporting it, saying there's something unusual here.'
The run took place in bright sunshine without incident this lunchtime. Hash House running began at a restaurant of the same name in Malaysia 80 years ago and has since become a world-wide movement.
In March, former Soviet spy Sergei Skripal, 66, and his 33-year-old daughter, Yulia, were poisoned by the nerve agent Novichok which had left on the door of Mr Skripal's home in Salisbury, Wilts.
In June, Dawn Sturgess and her partner Charlie Rowley were exposed to the agent in nearby Amesbury. Ms Strugess died the following mionth.
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