THE firefighters union wants the coroner to probe fears trainees were exposed to carcinogens that may have contributed to 15 deaths.

The union will today make a written submission to State Coroner Jennifer Coate asking her to inquire into chemical exposure at the CFA training college near Bacchus Marsh.

"We do not understand why neither the CFA nor the Government has referred this matter to the Coroner for investigation," UFU secretary Peter Marshall said.

The CFA began an investigation after the Herald Sun revealed firefighters and Fiskville locals had been exposed to carcinogenic chemicals in the 1970s and 1980s.

The CFA has been accused of not telling staff of the risks, even after a scientific report in 1990 revealed the deadly chemicals they had been exposed to.

Mr Marshall said the union had received legal advice that supported a coronial investigation.

The grounds are that 15 people may have died as a result of chemical exposure; waste was regularly collected from petroleum companies and used at Fiskville for live fire training; 200-litre drums are believed to remain buried at Fiskville; and claims that the CFA knew of the exposure danger from a 1990 report, but did not tell personnel or nearby residents.

"Only a coronial inquest or royal commission can properly test the truth of these and other matters that go to the heart of determining the extent of the exposure and any knowledge of the consequences to the health of individuals who were exposed," Mr Marshall said.

Coroners' Court spokesman Sheree Argento said the Coroner would need to consider whether she had jurisdiction, whether an inquiry was in the public interest, and whether broader public health-and-safety issues warranted further investigation.

The CFA said it was continuing to focus on its own investigation.

A State Government spokesman said it was satisfied with the independence of the investigation and the investigator: "We have said we are closely monitoring the investigation. We would intervene if necessary."

Read more on the Herald Sun.