Police are hunting for an arsonist they believe deliberately lit a fire near the Strzelecki Highway which spread to Hazelwood coal mine.
The fire has been burning for close to three weeks, and police say they are searching for an arsonist who may be at work in the area.
Victoria Police Chief Commissioner Ken Lay said the fire started on the Strzelecki Highway between Morwell and Mirboo North about 1.30pm on February 9.
The fire burnt through a timber plantation causing serious damage before reaching the mine.
There were also a number of smaller suspicious grass fires around the immediate area in Yinnar, Hazelwood and Boolarra on 28 January and again on the morning of 9 February.
Detectives believe person or persons lit "test fires" in order to understand how the fire would act.
Lay says the arsonists were "very calculated."
"They showed an absolute disregard to life and property," he said.
''This fire was set on the worst fire day this year and had the potential to cause an enormous amount of damage and loss of life.”
Investigators said the arsonists may still be active in the area and fear they will continue to light fires on days of high fire danger.
Inspector Mark Langhorn says locals may be responsible as the locations of the fires featured easy get-away routes that would have been known to the culprits, ABC reported.
"We believe there's a bit of a systematic arsonist and we really want to put a stop to this person very quickly," he said.
"It's our belief the person is well known or well familiar with the community.
"The locations of the fires are around dirt tracks or just off the highway.
"This wasn't necessarily kids fooling around, this was someone with a vehicle and mode of transport to light three fires within a 15 minute period.
"This is someone that has been planning."
Lay encouraged people in the Morwell community to “think back” to the day of the fire for any clues as to who lit the blazes.
''People don't wake up one morning on a day of very high fire danger day and decide they're going to light a fire. This is a pattern of behaviour that occurs, sometimes, over years and years and years. That's why it's important for the community to think back on that day,” he said.
Meanwhile 80 staff were evacuated from Hazelwood Power Station’s administration block yesterday afternoon as smoke from the fire entered the building.
The grassfire started about 4pm when it jumped from the coal mine and headed towards the power station.
A spokesman for GDF Suez, the station’s operator, said smoke forced the evacuation of 80 staff members.
"The power station is about 500 metres away, so it wasn't really under any threat," he said.
"Our concerns was not to allow any fire to get into the conveyers that take the coal into the power station.
“As a precaution, we took two of the generating units off for a short while."
The CFA downgraded the watch and act alert for the grassfire this morning and said crews had stopped the spread of the blaze.
While the coal mine fire is 50 per cent out, experts say it will continue burning for two weeks.
The fire is burning at two separate coal faces at the mine’s disused open cut site, with smoke hanging at low altitude in the Morwell community.
The EPA warns that the area will experience very poor air quality today and tomorrow, issuing a high level smoke alert for the Latrobe Valley as a result of the coal mine fire.
Victorian chief health officer Rosemary Lester said smoke could exasperate existing heart or lung conditions and cause irritated eyes, coughing and wheezing.
Residents concerned for their health have been advised to stay indoors and visit a health assessment centre at nearby Traralgon where assistance was available to anyone who needed help leaving the town, including fuel vouchers to visit relatives.
The Napthine government has been criticised for not evacuating the town as one of the fires at the site emits carbon monoxide.
'Everything that is required on the ground in terms of information and advice has been put in place,'' Health Minister David Davis.
''Vulnerable people … older people, pregnant women and, indeed, children, and also particularly those with respiratory conditions, were advised to seek support and attention from the relevant medical authority.''
The EPA’s air quality index for Morwell South, adjacent to the mine, was 125 between 9- 10am this morning. Anything more than 100 is considered ''poor''.
"PM 2.5 levels are at high levels and remain the primary risk, so it is important the community heed the advice issued by the Chief Health Officer each day during this incident,” EPA CEO John Merritt said.
For more information on the Hazelwood open cut mine fire: