Police were investigating a suspicious grass fire which started around 1am Wednesday at the rear of a factory on Lake Road at Stawell.
Stawell Country Fire Authority brigade was called out to the scene again at 7am to extinguish a re-ignition of the blaze.
District 16 Operations Manager Ian Morley said the fire was deemed suspicious and police were contacted.
“The cause was determined to be suspicious, so police attended the scene and will be continuing their inquiries,” he said.
Environment Protection Authority Victoria (EPA) chief executive Nial Finegan said a fire in the nine-million strong tyre yard would have significant ramifications.
He said tyre fires could cause major pollution of the atmosphere and were incredibly difficult to extinguish.
“Once ignited, they are very hard to extinguish and generate toxic smoke that could cause a health risk to the Stawell community and beyond,” Mr Finegan said.
He said EPA, in conjunction with other government agencies such as the Country Fire Authority, council and the Department of Environment, Land, Water and Planning, continue to work with UTRC in order to reduce the fire risk at the premises.