The Clerk of the Course for the Manx Grand Prix says he doesn't believe last night's diesel spill between Kirk Michael and Ballaugh was a deliberate act.
Several riders including Adam Barclay told Manx Radio they had suspicions about it.
Despite this, Phil Taubman says no competitors have reported any concerns to him.
However, he is renewing his appeal to drivers of diesel powered vehicles to make sure filler caps are locked tightly:-
Roads around the Mountain Course will close at six o'clock this evening for the latest practice session. They will reopen from Bray Hill at ten past eight.
And you can hear the full interview with Clerk of the Course Phil Taubman in Friday Sport at five past six this evening.