Hungary has asked for assistance from the European Union to help contain a flood of toxic sludge that has reached the waters of the Danube River.

In particular, the Hungarian government is seeking experts from other European states who can help "in dealing with the toxic sludge and decontamination," EU spokesperson Joe Hennon said by phone from Brussels Thursday afternoon.

The response should come "sometime pretty soon," he said, since EU countries were placed on alert in the wake of the disaster.

Meanwhile, Hungarian rescue agency spokesperson Tibor Dobson confirmed that the sludge had hit two parts of the Danube -- the second largest river in Europe -- by Thursday afternoon.

But officials within Hungary claim that the sludge that has reached the Danube is not toxic enough to be damaging, though Dobson said life in the country's Marcal River "has been extinguished" by exposure to more toxic portions of the sludge.

A 40-kilometre stretch of the Marcal River carried the sludge into the Raba River, which links into the Danube.

"This looks like one of the worst environmental disasters we've had in quite a while in Europe," Hennon told CTV News Channel.

"Priority number one is to stop it spreading, and after that we'll deal with why it happened and how it happened."

The overriding concern is that as the sludge enters the Danube, its toxic mass will flow south along the 2,850-kilometre long river into Croatia, Serbia, Romania, Bulgaria, Ukraine and Moldova, before making its way into the Black Sea.

Officials in Croatia, Serbia and Romania were taking frequent samples from the Danube on Thursday, hoping that the river's large volume would dilute the impact of the spill.

But Dobson said that the pH of the sludge that reached the Danube had been reduced to a point where it was unlikely to cause further damage.

Normal pH levels for surface water are typically between 6.5 and 8.5. Each pH number is 10 times the previous level, meaning a pH of 10 is 1,000 times more alkaline than a neutral pH of 7.

Dobson said the pH of the sludge hitting the river was below 10 and dropping. The country's National Disaster Management Directorate put the pH at 9.3.

Later Thursday, environmental chemist Gergely Simon of Clean Air Action Group, said he agreed that the diluted sludge that hit the Danube was not as dangerous as when it first spilled out of the reservoir.

"I know that is the case so it doesn't remain harmful for the Danube," Simon told CTV News Channel during a telephone interview from Budapest.

A disaster begins

The sludge disaster began Monday when a reservoir burst at a metals plant in Ajka, a town located about 160 kilometres southwest of Budapest.

Within hours, an estimated 1 million cubic metres of toxic waste were dumped into the environment, as it flowed into nearby villages that suffered heavy damage.

Whatever success authorities may have in limiting the damage to the Danube, there has still been major damage to Hungarian lands and rivers.

After visiting the three towns closest to the site of the spill on Thursday, Hungarian President Viktor Orban said there is "no sense" in rebuilding in the same location.

He also said affected residents have been left "desperate" and distrustful of Hungarian authorities since the toxic flood.

"There is no trust at all," he said. "The official reports said everything was okay."

In the nearby town of Kolontar, residents said the disaster had ruined the community that is home to 800 people.

"Those who can, will move out of Kolontar. From now on, this is a dead town," said resident Beata Gasko Monek.

After visiting Kolontar, the Hungarian president told state news agency MTI that the disaster "is so irresponsible that it is impossible to find words!"

Kolontar Mayor Karoly Tili said that only a week before the reservoir broke, Hungarian environmental authorities had said it was safe.

"People are scared," the mayor told The Associated Press. "People no longer trust or believe what is said about the reservoir."

Many are now seeking compensation from MAL Rt., the company that owns the plant where the disaster occurred.

The sludge stored in the reservoir is a byproduct of refining bauxite into alumina, which is used to make aluminum.

With files from The Associated Press