The alkali level of caustic red sludge now flowing into the Danube was below pH 9, so an ecological disaster had been averted, Interior Minister Sandor Pinter told a news conference Friday.

Meanwhile, an 81-year-old man died in a western Hungarian hospital on Friday morning, bringing the overall death toll from the million-cubic-meter spill to five.

Three people are still missing, and 150 were injured and treated in six different hospitals, including 11 rescue workers injured Thursday. Some of the injured remained in a life-threatening condition.

Government spokesperson Anna Nagy said the deluge of red sludge, an aluminum industry byproduct that engulfed three villages with a cascade of the highly caustic (pH 13) sludge when a containment reservoir wall broke on Monday, was the biggest ecological disaster to hit Hungary.

Pinter said police had already launched an investigation and were seeking people who had performed maintenance work on the containment barrier. At present, 4,000 people were participating in the clean-up process, assisted by about 300 vehicles, he added.

Pinter was unable to give the precise costs of damage control but acknowledged it would be in the billions of forints (millions of U.S. dollars).

He also announced the European Union would be sending a five-person team of experts to Hungary to ascertain the consequences of the red sludge spill. He declined to say when the Hungarian Aluminum Production and Trading Company (MAL), owner of the containment reservoir, would be allowed to resume production.

In Kolontar, one of the villages briefly submerged by the syrupy red mud, Damage Control Management spokesman Tibor Dobson reported that, by Friday morning, the pH value of the mud flowing into the Danube had been reduced to 8, a level deemed environmentally safe.

In another development, Greenpeace reported the arsenic content of the red sludge measured in Kolontar was double the level typical of red sludge. Greenpeace Hungary director Zsolt Szegfalvi said the arsenic level was far higher than had been cited in official reports -- 110 mg per kilogram according to Greenpeace measurements.