Firefighters say a fire which has been burning at the Hazelwood open cut coal mine in the Latrobe Valley for more than a month is now under control.

The fire, which broke out on February 9, choked the nearby town of Morwell with thick, foul-smelling smoke for two-and-a-half weeks, prompting authorities to urge vulnerable people to relocate.

Victoria's Fire Services commissioner Craig Lapsley has declared the fire is now controlled.

"There is no expectation of any further fire activity of any significance, and there won't be any fire moving out of the pit, is our estimate at this stage," he said.

But he said that while the fire was now controlled, the smoke would not clear up anytime soon.

"There will continue to be some smoke come out of the open cut periodically over the next few days and that could extend for at least a week or until at least we get good rains," he said.

"There are rains forecast this week for Wednesday and again on Saturday, and if those rains eventuate then we will be at the final stage of bringing this fire to its totality, where we can move the status from controlled to safe."

Vulnerable Morwell residents were advised to relocate from the town because of poor air quality and the Department of Health's chief health officer, Dr Rosemary Lester, says that advice will still stand.

At its peak, the fire blanketed nearby Morwell with thick, foul-smelling smoke. Some residents were forced to evacuate and others in town covered their faces with masks. ( ABC News )

"Due to the inversion conditions today we have unfortunately seen a reversion to poor air quality in Morwell, hence my advice that temporary relocation should still be considered, that advice stands we're not able to lift that advice at the moment," she said.

Dr Lester says conditions will be continually monitored in the coming days and weeks before that advice can be lifted.

The Environmental Protection Authority's (EPA) John Merritt says despite the status of the fire being downgraded, air quality will fluctuate.

"Air quality has been improving significantly over the last week we've seen it deteriorate today with these inversion conditions and we'd expect to see inversion conditions tomorrow morning as well," he said.

Lessons learned from open cut mine fire

Commissioner Lapsley says he hopes the incident will lead to a better understanding of how to deal with these sorts of fires.

"I've no doubt that this will be a catastrophic event that changes the way in which we deal with brown coal open cut events, and in particular those that are very close to communities," he said.

"We would be foolish not to pick up the learnings of this and take it to the next generation of how we deal with these.

"These open cuts are here to stay, they will be part of the Victorian landscape, and we need to make sure that the learnings are put into the future planning."

Commissioner Lapsley has also welcomed the Government's official inquiry into the fire and says he has also instigated his own inquiry into fire management of brown cut open coal mines.

Last week there were concerns for the safety of firefighters after the United Firefighters Union paid for independent testing on the water used to control the fire.

The occupational hygienist who carried out the test said it revealed extreme levels of E-coli and other dangerous bacteria which could get into small cuts and cause septicaemia.

Commissioner Lapsley then asked the EPA to broaden its testing regime to see if it could reproduce the same findings as the union's water test.