Volkswacht Bodensee - Evacuation orders lifted in Belgian wildfire zone

After being grounded by bad weather, water-dropping aircraft were back out helping to quell Belgium's largest wildfire in a century, after fire crews hacked their way through boggy terrain overnight to fully "encircle" the blaze.

Crisis cell spokesman Tony Hosmans told AFP the fire burning since Friday "has been contained and should no longer be able to spread" -- after threatening to spill over the German border to the east.

New flare-ups were still emerging across the vast site -- with the blaze smouldering underground in the peaty soil -- but were being "brought under control" one by one, he said, with the next goal to finally tame the fire.

Regional government spokesperson Stephanie Ernoux called the latest developments "reassuring", while the local governor's office said it was weighing whether to start scaling back the firefighting deployment on the ground.

Villagers in two Belgian hamlets were given the all-clear to return home, while the German town of Monschau also posted a notice telling residents living near the border it was safe to go back.

The High Fens fire grew over the weekend to half the size of Manhattan -- 3,000 hectares (7,500 acres) -- charring a huge expanse of peatland, pine trees and hiking trails, but hundreds of firefighters working night and day managed to stop it spread further.

On-site operations have been complicated by the fens' terrain -- a patchwork of heath, peat bogs and raised wooden boardwalks.

Aircraft flown in from Norway, Germany, Sweden and the Netherlands had been pinned on the ground by low-hanging clouds, but Hosmans said both helicopters and planes were able to resume operations Wednesday and were dropping water on the site.

- Zombie fire -

Europe has been swept by weeks of devastating wildfires fuelled by dry conditions and a historically hot summer, with France, Greece, Portugal and Spain also battling major blazes.

The High Fens blaze broke out for reasons still unknown in an area that was ravaged by massive fires in 1911, during a similar period of heatwaves.

It is the country's largest wildfire since.

Even once it is brought under control, officials have warned it will take weeks or even months of soaking and dousing to prevent the blaze from reigniting.

"The fire is burning in the peat, so it is actually underground, sometimes quite deep," explained area fire chief David Covens on a trip into the fire zone.

In peatland terrain like the High Fens, a fire can keep burning underground and resurface some distance away, a phenomenon known as a "zombie fire" that can also attack tree roots, increasing the risk of them collapsing.

"At first glance, it may seem under control, but it can flare up again because it re-emerges, sometimes from great depths," said the regional government's Ernoux.

To detect flare-ups more effectively, firefighters were using drones equipped with heat-sensing detectors, she said.

In forests, peat is an accumulation of spongy, highly flammable, carbon-rich material formed over time through the decomposition of plant matter.

It is an ideal fuel for buried embers, which can lie dormant until favourable conditions, such as wind and dry weather, allow them to reignite in broad daylight.

"Whenever we disturb the ground, when we cut down a tree and expose the soil, the fire can reignite," said fire chief Covens.

"We're doing everything we can with the resources available, but we know this is going to take a long time."

T.Germann--VB