Fears that Europe's second-longest river may be severely polluted by a flood of red toxic sludge were eased Friday, after officials reported that toxic heavy metals in water flowing into the Danube had receded to levels permitted in drinking water.

The flood of red sludge has coated a swath of rural Hungary and is nearing the size of the Gulf oil spill. But officials say the toxic mess is actually causing little immediate harm.

Government officials said Friday 696 million litres of sludge poured into three villages when a reservoir broke at an alumina plant early this week. BP's spill last April gushed about 757 million litres of oil into the Gulf of Mexico.

In Hungary's case, however, the environmental consequences "do not seem to be that dramatic," said Philip Weller, the head of the International Commission for the Protection of the Danube.

The river is absorbing the sludge and the threat has been eliminated, Prime Minister Viktor Orban said.

"We managed to take control of the situation in time."

Monitors were taking samples every few hours Friday where the sludge was flowing into the Danube, which continues through Croatia, Serbia and Romania. Test results released by Hungary's disaster agency revealed a pH level of 8.2, which is considered a safe alkaline level.

Localized disaster

The tests suggest that the Danube's enormous flow of water may help it escape the fate of smaller rivers and streams closer to the spill site, which have been crippled by the toxic sludge.

By contrast, Greenpeace released findings from a laboratory analysis of sludge samples taken closer to the spill site, which showed high concentrations of toxic substances.

The environmental organization said there is a risk the sludge in the area could cause pervasive and long-lasting damage.

The findings showed "surprisingly high" levels of arsenic and mercury. About 50 tons of arsenic, 300 tons of chrome and half a ton of mercury leaked into the ground as a result of the spill, Greenpeace officials told reporters in Vienna.

They also found arsenic levels 25 times the limit for drinking water after taking a sample from a canal near the spill.

Meanwhile, Hungary's state secretary for the environment expressed concern about the area's air quality.

"Wind can blow ... that heavy metal contamination through the respiratory system," said Zoltan Illes.

Residents living in the area were warned about the potential threat and were asked to wear face masks. However, they have not been asked to stay away from the area.

Some residents said they were taking heed, despite reassurances from the Hungarian Academy of Sciences that the heavy concentrations of metal are in fact not an environmental danger.

"The academy can say whatever it wants," said Barbara Szalai Szita, who lives in Devecser, one of the hardest-hit villages. "All I know is that if I spend 30 minutes outside I get a foul taste in my mouth and my tongue feels strange."

An 81-year-old man also reportedly died Friday morning from unspecified injuries sustained in the flooding.

Cause probed

Officials were still investigating what caused a section of the reservoir to collapse. More than 150 people were injured during the incident, many by chemical burns. Seven people died and 10 people were in serious condition. One person reamed missing.

A massive cleanup of the area continues but officials have warned residents that it will be some time before they are allowed back into their homes, CTV's London Bureau Chief Tom Kennedy told CTV News Channel from the affected area.

A second industrial reservoir at the spill site Friday was also drained to prevent a new disaster.

Media access to Kolontar, the area closest to the leak, was restricted on Friday. Officials said the large presence of reporters and TV crews was interfering with the clean-up process. Members of the press were allowed access three times a day, accompanied by minders.

The red sludge entered the Danube on Thursday after devastating creeks and rivers near the spill site. It continued to move downstream Friday toward Hungary's immediate neighbours, Croatia, Serbia and Romania.

The sludge has not only damaged some infrastructure but it has soaked the earth.

Hungary has asked the European Union for technical experts to help them deal with the disaster.

With files from The Associated Press