Police are reminding people not to enter closed roads during racing, after reports of someone crossing the course at St Ninian's.
A man was seen breaking closure restrictions during yesterday evening's Manx Grand Prix qualifying session, Tuesday, August 19.
Officers say the incident could have ended "horrendously".
They add they will continue to work with marshals to prosecute anyone who sets foot on closed roads, particularly where this puts people are at risk.
A local man is currently helping police with their enquiries into the matter at their Douglas Headquarters.
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