There are fears similar carcinogenic chemicals were also used at other training areas, including Penshurst.

Hundreds of professional and volunteer firefighters from the region spent weeks at the Country Fire Authority’s (CFA) complex near Ballan in the 1970s and ’80s, when chemicals were burnt as part of training techniques.

Several have already expressed fears about their own involvement.

Long-serving CFA officers around the state, including one from the south-west, have since contracted cancer, but no clear causes have been determined.

The Standard understands the serving south-west officer who recently was diagnosed with cancer trained and worked at Fiskville, but was also exposed to chemicals while fighting bushfires.

The CFA this month launched its own investigation, appointing former Environment Protection Authority deputy chairman Robert Joy as independent chairman.

However, the United Firefighters Union wants a full, independent coronial hearing without the risk of a cover-up.

Union state secretary Peter Marshall said yesterday a “significant” number from the south-west had contacted his organisation expressing concerns and volunteering information about training practices.

“We are very concerned,” he said. “The more we hear and information received indicates this is just the tip of the iceberg.

“They are saying the same sorts of carcinogenic chemicals were burnt at other training centres, but I can’t say specifically where.

“There would be 50,000 volunteers who would have an interest in this issue,” Mr Marshall said.