A third person has died in flooding caused by the rupture of a red sludge reservoir at an alumina plant in western Hungary, rescue services said Tuesday. Six people were missing and 120 injured in what officials said was an ecological disaster.

The sludge, a waste product in aluminum production, contains heavy metals and is toxic if ingested. Many of the injured sustained burns as the sludge seeped through their clothes. Two of the injured were in life threatening condition.

The chemical burns caused by the sludge could take days to reveal themselves and what may seem like superficial injuries could later cause damage to deeper tissue, Peter Jakabos, a doctor on duty at a hospital in Gyor where several of the injured were taken, said on state television.