Concerns have been raised by the Environment Protection Authority who are investigating whether a pile of 30,000 tyres that caught fire was illegally dumped.

EPA acting chief executive Chris Webb said fire remnants could potentially harm local waterways and endanger nearby communities.

He said the investigation would initially focus on the immediate clean-up and containment of fire remnants.

"The remains are huge quantities of steel radials and rims that are likely coated in harmful residue, which we do not want entering local creeks and rivers," Mr Webb said.

"EPA is now in the process of advising on how best to capture any runoff with over 100mm of rain predicted over the next few days."

Ararat Police Crime Investigation Unit are also investigating the incident, however no charges have been laid.

Mr Webb said stockpiled tyres were a fire hazard waiting to happen.

"Tyre fires are very difficult to control and generate toxic smoke, which can cause health risks through the inhalation of particulates and chemicals," Mr Webb said.

He said illegally dumped tyres was an ongoing issue in Victoria, with up to six million car tyres "unaccounted for".

Strict rules surround tyre storage, with stockpiles larger than 5,000 units requiring work approvals and licenses from the EPA.

Country Fire Authority (CFA) District 16 operations manager Chris Eagle said last week that authorities had monitored the spread of smoke from the fire last week and at the time it had only been travelling a few hundred metres before dispersing.

"We've been closely monitoring where the smoke is travelling and how far it is going and we're happy at the moment that there is no effect or impact on the residents here in town," Mr Eagle said.

The community is encouraged to report pollution to EPA on 1300 372 842 or by visiting www.epa.vic.gov.au