EU experts to tackle Hungary toxic sludge
Experts from the European Union are to begin work in Hungary to tackle the toxic sludge spill that has claimed seven lives and devastated large areas.
The civil protection unit will work on restoring affected areas and assessing further risks.
The main concern is how to lessen the impact of a new burst in the reservoir, which officials say is inevitable.
A protective ring of rock and earth is hurriedly being built to try to beat the expected next torrent.
In addition to those killed, some 150 people were injured after up to 700,000 cubic metres (24.7m cu ft) of the toxic aluminium by-product burst from the reservoir near Ajka in western Hungary on 4 October.
The BBC's Nick Thorpe in Ajka says the EU experts were specially requested by Hungary, which has been struggling to understand the environmental and health consequences of the red mud, which covers an area of around 40 sq km (14 sq miles), including several towns and villages.
The mud is the residue of years of production of aluminium oxide.
It has a very high alkaline and heavy metal content and our correspondent says the first task of the international experts will be to assess its danger to the ground water, the soil and as an airborne health hazard as the toxic mud dries out.
The five-member civil protection team will later try to restore the natural environment in the devastated areas and try to prevent further threats.
"The quick selection of this team... clearly shows that European solidarity is working," EU crisis response commissioner Kristalina Georgieva said.
The major concern is the second reservoir rupture.
Environment State Secretary Zoltan Illes said on Sunday the collapse was inevitable.
It is hoped that the protective ring of rock and earth, 600m long and 30m thick, which is being built across the fields just below the reservoir, will contain any new spill.
Speaking from the site, Mr Illes said: "The collapse could take place right now, tomorrow, the day after tomorrow, but who knows?"
Pointing to the possible point of rupture, he said the failure of the wall there could release "five to seven million tonnes of red mud".
"That embankment, if I could gain three days, that embankment can halt any new tsunami of red mud."
Peter Szijjarto, a spokesman for Prime Minister Viktor Orban, told local television on Monday that officials hoped to have the emergency wall built by Tuesday.
"We have 4,000 people and 300 machines working at the scene so we are doing our utmost to prevent another tragedy," he said.
Our correspondent says that officials are also hoping there will be no more rain, as that could turn the sludge more liquid and make containment more difficult.
The new spill could affect an area up to one kilometre to the north if not contained.
Thousands of residents of Devecser have been told to be ready to evacuate at short notice.
The government in Hungary is also expected to decide on Monday whether the factory can restart production.
The company, MAL Hungarian Aluminium Production and Trade Company, has expressed condolences to the families of the victims but is under investigation by Hungarian police.
Mr Illes said the company faced fines for environmental damage that so far total almost $100m.
The sludge has a caustic effect on the skin. It contains heavy metals, such as lead, and inhaling its dust can cause lung cancer.
Most of those killed were drowned or swept away in Kolontar as the sludge hit.
All life in the Marcal river, which feeds the Danube, is said to have been extinguished.
The sludge reached the Danube on Thursday, but Hungarian officials said on Friday that the pH level in the river was "normal", easing fears that Europe's second longest river would be significantly polluted.
Emergency crews have been working to dilute the alkaline content of the spill, adding huge quantities of gypsum and chemical fertilisers to the waters of the Marcal and Raba rivers.