The regional chief of Hungary's disaster relief services has said pollution levels from a sludge spill have declined and the Danube has suffered no obvious damage so far.
Tibor Dobson said the latest information showed pH levels of 8-8.2 in the Danube, which could be considered 'normal'.
That level is down from a level of around 9 when the sludge reached the river yesterday morning.
'These data give us hope ... and we have not experienced any damage on the main Danube so far,' Mr Dobson said.
Teams of workers have attempted to reduce the alkaline content of Monday's spill from a containment reservoir of an aluminium plant.
Mr Dobson said there have been reports of sporadic fish death in the Raba and Mosoni-Danube rivers in western Hungary.
The spill's alkaline content when it reached the Raba, the Mosoni-Danube and the Danube rivers yesterday was still around pH 9, above the harmless range of 6-8.
All fish had died in the smaller Marcal River, which was struck by the spill first with much higher alkaline levels.
Crews are monitoring water quality on the Danube as the pollution moves downstream towards Budapest.
Hungary declared a state of emergency in three counties on Tuesday after the sludge hit Kolontar, Devecser and other villages 160km west of Budapest.
The death toll from Monday's disaster meanwhile rose to seven, officials said.
In the villages swamped by sludge, disaster crews, military and local villagers are clearing away the rubble and continue to search for three missing people.
Many people suffered from burns and eye ailments caused by the caustic effect and corrosive elements in the mud.
The company at the centre of leak has defended itself.
In a statement on its website, MAL Hungarian Aluminium Production and Trade Company said that it had released €110,000 in aid to local authorities to help deal with the disaster.
According to the mayor of one of the villages worst hit by the sludge, the sum would go to payments of €360 to each family affected by the leak.
In its statement, the company also offered its condolences to the relatives of the four people who had died and said it would cover their funeral expenses.
MAL has come under fierce criticism, with officials suggesting too much of the caustic red sludge was contained in the reservoir, but the company insists it has done nothing wrong.
It said it was devoting 'all its energies and efforts' to alleviating the effects of the spill.
The Danube runs from Hungary through Croatia, Serbia, Bulgaria, Romania and Ukraine to the Black Sea.
Serbia, Croatia and Romania said they are stepping up monitoring of the river given the risk of drinking water contamination in towns along the river.
