The fire followed a large party held at a holiday cottage at Kilgram Farm in Jervaulx during the early hours of Sunday, September 9.
North Police today said that two men had been seen talking between a Dutch barn and a barn containing livestock.
The men were shouted at by the owner of barns, who told them to move.
A spokesman said: "Officers are appealing to these two men to come forward as they could have important information that could assist the investigation."
Also in news: National Park officials ‘too fond of saying no’The men or anyone who knows their identity are asked to email [email protected] or call the force on 101, select option 2 and ask for PC Michaela Godridge.
Information can also be passed on anonymously to Crimestoppers on 0800 555 111.
Anyone passing on information is asked to quote reference 1218016864.