(CNN) -- Five European Union experts are due to arrive in Hungary Monday to find out how badly toxic sludge has damaged the environment and advise on decontamination, the EU said.
Meanwhile, Hungarian authorities continue frantically building dikes in case the dam holding the sludge breaks further, the government said Monday.
A "large section" of the dam is still showing signs of ruptures, the government said in a statement, meaning there is a "continuing risk of a possible spill".
The area has been evacuated and soldiers were on standby Sunday, an official said.
The cracked wall is expected to collapse, Gyorgi Tottos, spokeswoman for Hungary's Catastrophe Protection Directorate, told CNN Sunday. "We know that it will happen," she said, although when is unknown.
About 8,000 people have been evacuated from the village of Kolontar, leaving it essentially empty, she said. Hundreds of soldiers were at the ready to rescue inhabitants of a nearby village when the wall collapses.
A 50-cm (19-inch) crack has developed in the wall of the aluminum plant reservoir. If the wall collapses, 500,000 cubic meters of toxic red sludge could spill out. That's about half the amount that spilled last Monday, inundating Kolontar and two other villages. Seven people were killed and more than 100 injured.
CNN
