Archaeologists found the illegal distillery on a dig at Ben Lawers National Nature Reserve near Killin.
Certas Energy says other possible explanations for the leak at the Gulf fuel station at Lix Toll have emerged.
The water supply to households in Killin was disrupted after an incident at a petrol station on Friday.
Volunteers have handed out about 40,000 bottles of water since the spillage, which a local petrol station blamed on an attempted fuel theft.
The Scottish Environment Protection Agency has warned that fuel contamination in the River Dochart may have spread to the River Tay.
Residents in the village of Killin reported a solvent smell and taste to their water on Friday.
A fuel spillage contaminates a river and water supply for the village of Killin.
Cold air carried on strong winds from Iceland has resulted in the chilly weather.
The 67-year-old died at the scene of the collision near Lawers on Friday.
