Residents of a Hungarian town remain on alert for possible evacuation amid fears of a potential new leak from the reservoir that spilled toxic sludge last week.
Police regulated traffic at a checkpoint near the entrance of the town of Devecser as trucks sprayed water to clean up the roads.
At least 300 military personnel have been deployed to the area along with around 130 transport vehicles, and five trains are on standby in case of evacuation orders.
Last Monday, about a million cubic metres of red mud, a by-product of alumina production, leaked out of an alumina plant reservoir into villages and waterways in the area, killing seven people, injuring 123 and contaminating rivers.
The cause of the accident remains unknown.
Gusztav Winkler, a professor at the Budapest Technical University, helped examine the area's soil 30 years ago, and explained that a poor choice of location may be partly to blame.
He said two different soils meet here, one of sediment type and one of clay.
"If the precipitation or ground water grows on this wet land then the two different types of soil move very differently. The move can be of several centimetres and it can cause tensions in the rigid surface of the dam which is a cemented slag unit and can break under certain circumstances."
It is not clear what might happen to the dams, which Winkle says should be monitored closely as soil under the entire basin is capable of serious shifts.
Winkle warns that once the system is broken at one place, it's impossible to know what will happen.
A team of EU experts is being sent to Hungary to help authorities deal with the disaster.