Pollution levels from a red sludge spill in Hungary have declined and the Danube, one of Europe’s longest rivers, has suffered no palpable damage so far, a spokesman for Hungarian disaster crews said on Friday.

Tibor Dobson said fresh data showed pH levels of 8-8.2 in the Danube, which could be considered “normal,” down from a level of around 9 when the sludge reached the river on Thursday.

“These data give us hope … and we have not experienced any damage on the main Danube so far,” Dobson told Reuters. Crews have strived to reduce the alkaline content of Monday’s spill from a containment reservoir of an alumina plant.