(CNN) -- Authorities were evacuating a Hungarian village Saturday after they found new damage in the reservoir that caused a toxic sludge spill this week, an emergency services spokeswoman told CNN.
Hungarian Prime Minister Viktor Orban, who was visiting the stricken area Saturday, said it was "very likely" the reservoir wall will collapse.
"It's in very bad shape, and our estimation is that that wall could fall down," Orban told reporters in the town of Ajka. "One consequence is that human lives could be in danger. That's the reason why we pulled out ... all human lives from that area, in order not to have more loss in human life."
If the wall collapses, 500,000 cubic meters of red sludge could spill out -- half of the amount that spilled out Monday, the prime minister said.
All residents of Kolontar village were being evacuated, spokeswoman Gyorgyi Tottos said. Previously, only the residents of a few affected streets had been told to leave, she said.
The sludge inundated Kolontar and two other villages after the aluminum plant reservoir burst, killing seven people and injuring more than 100, officials have said.
Specialists were working Saturday to reinforce the reservoir and take necessary measures to prevent another toxic spill, Tottos said. The reservoir had been repaired after the disaster and the flow from the pool halted.
The sludge reached Europe's mighty Danube river on Thursday, raising fears of wider contamination in Hungary and countries downstream, including Croatia, Serbia, Bulgaria, Romania and the Ukraine.
Water test results released Friday, however, indicated the sludge may not harm the Danube after all. The pH, or acidity, level of the Danube water was 8.5 on Friday -- slightly above normal but not dangerous and able to sustain life, Tottos said.
Readings of pH range from 0 to 14. Levels lower than 7 characterize acids, and levels higher than 7 denote bases; highly acidic or highly basic water can harm living things.
The 8.5 pH level and fast-moving currents made officials optimistic that a natural disaster can be avoided, she said.
The environmental disaster occurred near Ajka, nearly 100 miles west of Budapest. The sludge covered the villages of Kolontar, Devecser, and Somlovasarhely, in some places reaching several feet high, leaving dead animals such as fish and frogs in its wake.
Orban warned of the "toughest possible consequences" for those responsible for the spill and said human error was the cause.
"Behind this tragedy, some human errors and mistakes must exist," he said. "We will reveal all of that, and the consequences will be very serious -- as much as you can imagine."
In addition to all the residents of Kolontar, about 500 residents of Devecser and the residents of 16 homes in Somlovasarhely have had to evacuate, Tottos said.
The exact chemical composition of the sludge has not been revealed, but aluminum processing normally involves compounds that include cyanide, cadmium and chromium.
Emergency workers have been pouring plaster and fertilizers on the sludge in hopes that it will counter its alkalinity. Dust from sludge that dries may also pose a threat, Hungary's Interior Ministry has said. It said some workers involved in damage cleanup may need filtering masks.
CNN's Mila Sanina and journalist Flora Hevesi contributed to this report.