Investigators have uncovered another illicit toxic dump in Melbourne’s north, the eighth property involved in what authorities have called "highly co-ordinated ... highly organised illegal activity” in the hazardous waste industry.

Sources say inspectors from the Environment Protection Agency and WorkSafe discovered the apparently derelict property in Campbellfield on Wednesday.

Graham White at the site of one of the illicit chemical dumps in Epping on Wednesday Credit:Darrian Traynor

It is now under 24-hour guard amid concerns the potentially highly-flammable contents make it a potential target for arson or at risk of catching fire in the summer heat.

The Age has confirmed this latest dump site is also linked to Graham Leslie White, the Wallan-based businessman connected to the stockpiles in Epping and Campbellfield and the heavily contaminated factory in West Footscray that burned down last year.