Authorities in Matera, which is popular with tourists for its ancient sassi or cave dwellings, say that levels of coliform bacteria – the group that includes E. coli – exceeded safe levels in some of the samples tested from water used to fill local taps.
The mayor's office issued an urgent warning on Friday morning advising people not to drink water from the mains until further notice.
It also ordered the city's schools to remain closed throughout the day.
In the meantime water company Acquedotto Lucano will be responsible for distributing bottled water, Mayor Raffaello De Ruggieri's statement said.
Coliform bacteria is found in human and animal waste, as well as soil. While most types are not harmful, the species known as E. coli can cause serious illness, though it is only rarely transmitted via contaminated drinking water.
However, high levels of coliform bacteria can be an indicator that waste has reached the water and therefore other harmful bacteria are likely to be present, which is why health authorities consider it a warning sign.
Contaminated water in industrial cooling towers was blamed for a recent outbreak of legionella, the bacteria that causes Legionnaire's disease and other sicknesses, in northern Italy.
Photo: Fabrice Coffrini/AFP