The tracked excavator was used to damage other equipment at the site and then crashed and set ablaze resulting in Devon Fire and Rescue attending the Devonport site last Thursday.

Police said that they were taking the matter very seriously. Sgt David Eamesare said he had launched an arson investigation into the incident, which caused £90,000 of damage.

“As well as the significant financial loss, I am also concerned about the safety of the individuals who have qualified themselves to drive such specialist machinery,” he said.

“Although it may be appealing, driving a digger could result in serious injury and it is incredibly fortunate no one was hurt during this incident.”

The excavator belonged to Landscape Matters Ltd

German company MVV is building the controversial plant, with Kier carrying out the main construction package. The plans faced fierce opposition from locals but was given the go-ahead despite council opposition.

The Devonport site will produce electricity and heat by burning rubbish from Plymouth and much of south and west Devon and is due to start operating in 2015.