Authorities say the Princes Freeway, in south-east Victoria, could remain closed for three months because of concerns about a possible landslide.

The freeway was closed at Morwell last night due to concerns about the stabililty of a nearby mine.

The north side of the mine, adjacent to the highway, has become unstable after recent heavy rain and movement has been detected in the mine wall.

That part of the mine has been decommissioned and International Power says it will not affect the operation of the Hazelwood power station.

VicRoads says cracks of up to two centimetres have emerged from the freeway.

The Energy Minister, Michael O'Brien, is unable to say when the highway will be re-opened.

"We've got some experts on site now keeping an eye on things," he said.

"But just out of an abundance of caution, the decision has been taken by VicRoads in conjunction with Victoria Police and my department to close the Princes Freeway, to ensure the stability and integrity of the roadway."

Superintendent Geoff Newby from the Gippsland Police says meetings will be held with mining experts and emergency services this morning.

Local residents have been called to a public meeting tonight.

Shut down

Environmentalists want the plant to be shut down.

Mark Wakeham from Environment Victoria says it highlights the real safety and sustainability problems with coal fired power.

Mr Wakeham says the risk of subsidence was raised five years ago when the coal mine was being expanded.

"We need to see a clear plan from the Coalition for a phasing out of the Hazelwood Power Station and mine.

"They've set a target for Victoria to reduce greenhouse gas emissions by 20 per cent by 2020. As yet they have no strategy for achieving that target and replacing Hazelwood is a good starting point."