Police have interviewed three teenage boys in connection with a suspected arson in Mabe.
The barn at Antron Farm, between College Reservoir and Argal Reservoir, went up in flame on October 21.
A spokesperson from Devon and Cornwall Police said: "Police were notified of a fire which is reported to have happened between 3pm and 3.50pm on Sunday 21 October in a barn on Antron Lane, Mabe Burnthouse, Penryn. The fire is currently being treated as arson.
"Police were called by fire who attended where a large fire had taken hold of the barn. It’s believed that a large quantity of hay, along with equipment and tools were damaged during the fire.
"Three boys aged 15, 15 and 16 voluntarily attended a police interview and investigations are ongoing."
Further appliances from Truro and Tolvaddon attended, also in attendance were the water carrier from Helston and support resources from St Just and St Austell.
A further appliance from Truro arrived at the scene around 5pm, after the roof of the building is believed to have collapsed.
Firefighters wearing breathing apparatus used jets at the scene, while ground monitors were used to extinguish the fire.
Some fire crews left the scene at 8.30pm, however, appliances from Falmouth and St Austell remained on scene to monitor the situation until it was deemed safe.
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules here