Concerns have emerged in the wake of a significant factory fire in Melbourne's west.

Although the fire at Derrimut has been brought under control, water contamination is now being investigated, as runoff containing unknown chemicals from the fire site has entered local waterways.

Fire Rescue Victoria (FRV) reported that the blaze, ignited by a chemical explosion around 11 am on July 10, was subdued by approximately 3:30 pm.

More than 180 firefighters responded to what has been characterised as one of the largest fires in Victoria in recent years. 

Authorities have issued warnings for residents to avoid contact with waters downstream from the fire, particularly in areas with unusual odours or discolouration. 

Melbourne Water says it is handling a significant volume of contaminated runoff that has entered Kayes Drain to the west of the factory and Cherrys Main Drain to the east.

The fire allegedly broke out at the ACB Group factory - the site of a fatal chemical explosion last year - and is under investigation by WorkSafe. Since the explosion, investigators have visited the site 24 times, issuing seven compliance notices.

The Environment Protection Authority (EPA) has reportedly conducted nine inspections since last year's explosion and issued several notices to the factory operators. 

Environmental experts have expressed concerns over potential health implications from the chemical runoff. 

Dr Sally El Meragawi, a chemical engineer from Monash University, said there are major risks. 

“Contamination from fires at chemical storage sites can include substances such as per- and polyfluoroalkyl substances (PFAS), heavy metals, and more. These chemicals can have serious long-term impacts on health and the environment,” she stated.

El Meragawi noted that PFAS chemicals, commonly found in firefighting foams, are particularly problematic.

Roger Read, an Honorary Associate Professor in the School of Chemistry at the University of New South Wales, also highlighted the dangers posed by the runoff. 

“The fire's black smoke and orange flames indicate the combustion of heavy oils and solvents, which generate toxic particulates and other hazardous materials in the smoke and water runoff,” he said.

Further investigations by the EPA and WorkSafe are underway to determine the full impact and necessary regulatory responses.