Hundreds of thousands of people in New South Wales face a growing bushfire calamity, with fires across a large swathe of Sydney's western edge in danger of linking up.

With the threat of the entire Blue Mountains area as well as Penrith and Richmond burning over the next few days, state Premier Barry O'Farrell on Sunday took the extraordinary step of declaring a state of emergency across NSW for the next 30 days, which will give special powers to all emergency services to deal with what could be a catastrophe.

Mass forced evacuations affecting tens of thousands of people are possible as hotter and drier than expected conditions combine with huge fire fronts already burning.



''This is not out of the realms of possibility,'' NSW Rural Fire Services Commissioner Shane Fitzsimmons said.



''We are expecting the potential for the series of these fires to come together, to extend right down Bells Line of Road.



''They have the very real potential to go right out to the eastern end of the Hawkesbury, right down into the north-west area of Sydney including Richmond.



''That's what we are talking about, the run from Bilpin right through to Richmond.



''We are also talking about the fires coming down the northern areas of the Great Western Highway, everywhere from Blackheath to Katoomba, Leura and all the townships all the way along to places like Springwood and Winmalee.



''That's the magnitude. I sincerely hope it's not realised and we end up somewhere in between, but what we can't ignore is the probability, based on the weather forecast and based on the current fire behaviour that we've experienced and which we are continuing to experience across these fire grounds.''





On Monday morning, an emergency warning was still in place for the 37,000-hectare State Mine fire, which started on Defence land near Lithgow.



An investigation is yet to determine whether it was ignited by explosives training.



The Rural Fire Service said the fire was burning near the township of Bell, as well as Dargan, Clarence and Bilpin.



An emergency alert telephone warning message was sent on Sunday to residents in Bell, who were advised to leave their properties immediately if not prepared and travel west along the Bells Line of Road towards Lithgow.The Lithgow Workers Club is open as an evacuation centre.



On Monday morning there were 63 fires burning around the state, with just one emergency warning and three ''watch and act'' warnings for fires at Springwood and Mount Victoria in the Blue Mountains and Balmoral in the southern highlands.



The weather is expected to be at its worst on Wednesday, with the forecast for high temperatures, low humidity and high winds being assessed as much worse than predicted last week.



''We are not in a catastrophic [weather] ratings scale [but] we are talking about fire danger ratings that will be in the severe category - and you overlay that with the fires that are already burning and it's a whole new ball game,'' Fitzsimmons said.



The worst fire disaster in NSW for at least 45 years could lead to evacuations from high-population centres such as Katoomba and Leura.



The state of emergency powers gives emergency services authority to deal with ''whatever eventualities may arise'', O'Farrell said. This included the right to order the public to leave or to enter an area and the right to demolish a building.



It also prevents people from disobeying an order given under these powers, making it an offence to obstruct or disobey these orders.



Already, the official NSW property toll is 208 homes destroyed and 122 damaged. A 63-year-old man has died fighting the fires and there have been 610 insurance claims for damage estimated at A$43 million (NZ$48.97m), a number that is expected to rise significantly.



Assistant Police Commissioner Alan Clarke said: "Let me say this: police will be doing forced evacuations if necessary."



O'Farrell conceded this would undoubtedly cause distress to some people but said: ''At times like this, it's better to be safe than sorry."



Fitzsimmons added: "I'm sure it will be [controversial]. There isn't much in the fire-management business that isn't controversial ... But I'd rather be copping criticism in two or three days' time for what didn't occur."



After a briefing at the RFS headquarters at Lidcombe, O'Farrell said the destruction of 208 homes might ''not be the end of it" so people in targeted areas would be asked to leave their homes.



That process began on Sunday when the residents of the village of Bell in the Blue Mountains were advised to evacuate.



So were more residents west of Bilpin village, including the communities of Mount Tomah and Berambing, who were told to leave along the Bells Line of Road towards Richmond.



In Bilpin, residents were told they could choose to stay but were warned power was likely to be cut and they might be unable to leave the town for days because fires would block roads in and out.



But O'Farrell said: "If the choice is life or property, the choice clearly should be life."



Clarke said emergency services would provide as much information as possible for people to save their properties but he appealed for them to evacuate as soon as that advice was issued. "At the end of the day, we hope we have buildings standing, but if we don't have buildings standing, we don't want bodies in them," he said.



''It's important to understand that the single tragedy we've had in these fires so far has been ... where an individual chose to remain and fight a fire.''



Emergency services could not tie up resources ''wrestling with one person to get off a property if they are capable and able to make a decision''. They needed to focus on people who couldn't help themselves, he said.



Fitzsimmons said it was always dangerous to draw parallels but "you'd be going back to time periods in the late '60s, where the '68 fires would be close" to the present situation.



"The reality, however, is these conditions that we're looking at are a whole new ball game and in a league of their own," he said. He warned the entire Blue Mountains community needed to be on alert for possible evacuations, from Mount Victoria and Blackheath to Katoomba and Leura, "right down to the fire burning in Springwood" and beyond to Kurrajong and Richmond.



"We are not talking necessarily at this stage of mass evacuations of the entire Blue Mountains community," he said. "But what we can't rule out is that there will be parts that may well so be evacuated. We have very changing, dynamic, volatile situations that will unfold over the next three to four days."



Asked how evacuations would work, if necessary, in the bigger population centres of Katoomba or Leura - where the Great Western Highway, the only major escape route, could be a traffic jam in the best of conditions - Fitzsimmons said those strategies were now being considered.



Fitzsimmons said light rain expected on Tuesday would be "inconsequential" and any marginal improvement on the extreme weather that triggered the initial fire disaster last Thursday would be "academic" now that fires were burning over such vast terrain.



"When you overlay that fire weather forecast across [the Lithgow fire] ... and an active fire edge of more than 300 kilometres, and you couple that with a fire only several kilometres to the south near Blackheath, and indeed a fire where we've seen so much devastation already down towards Springwood and Winmalee, we've got what would be unparalleled in terms of risk and exposure for the Blue Mountains and Hawkesbury communities throughout this week."