An outbreak of toxic algae in the Murray River is spreading rapidly, with the size of the bloom doubling in the space of 48 hours.
More than 680 kilometres of the river is on the highest level of alert, after river managers increased warnings yesterday.
The ''red alert'' now stretches from Wodonga to Barham, affecting major towns in between such as Yarrawonga, Cobram and Echuca.
Under a red alert, people are advised to have no contact with the river or risk gastroenteritis, eye and ear complaints.
The same towns were affected for weeks by a massive algal bloom last year, and Environment Victoria spokeswoman Juliet Le Feuvre said outbreaks were becoming too common.