Arson is suspected after Cornwall Fire and Rescue Service were called to a polytunnel fire at a farm near Penzance on Saturday morning.
A fire crew from Penzance was called to the farm at Higher Trevaylor, near Gulval, at around 1am.
Upon arrival the crew found the polytunnels extinguished.
There have been no reports of any injuries.
Devon and Cornwall Police have been informed and will be making further enquiries.