The open cut mine was not properly rehabilitated after it was closed 30 years ago and is now leading to extensive cracking after recent inundation in the state, the Construction, Forestry, Mining and Energy Union’s Luke van der Meulen said.

The Victorian Department of Primary Industries had failed to properly regulate the mining industry in the Latrobe Valley and should have ordered the mein to be filled in, he told ABC radio.

"I think the Department of Primary Industries has a lot to answer for," van der Meulen said.

"They're responsible ... and had this rehabilitation always been part of mining in the Latrobe Valley then we wouldn't have these problems and I think the DPI needs to get on and make the rehabilitation of the mines as big a priority as opening up of new areas and new mines."

A spokesperson for International Power Hazelwood said the company was continuing to undertake a range of comprehensive monitoring at various sites along the northern part of the mine, close to the freeway.

Results of this monitoring activity were regularly reported to the DPI and incident response team, he said.