Rome - Authorities in Italy suspect some 70 million litres of cheap wine on sale in local shops and supermarkets could contain illegal, harmful substances, a weekly magazine reported Friday.

And in a separate report that threatens to harm the image of one of Italy's most prized vintages, L'Espresso magazine also said a probe is underway on an alleged scam to mislead consumers by falsely labelling bottles.

But Agriculture Minister Paolo De Castro played down the reports saying that the investigations showed Italy has "serious controls in place and we can demonstrate this with the facts."

De Castro also said that the amount of wine found to have contained illegal substances amounted to less than 1 per cent of Italy's total production.

The investigation on the chemically altered wine stemmed from a September 2007 raid on a producer in Veronella, in the north-eastern Veneto region, L'Espresso said.

Canisters of sulphuric acid found during the operation prompted authorities to confiscate wine from the producer's cellar.

Test results showed that the wine seized contained only between 20 and 40 per cent of permitted natural substances with the rest made up of illegally added sugar but also fertilizers, manure and several acids, aimed at raising alcohol content.

The illegal substances can "over time" threaten the health of consumers including cancer, L'Espresso said.

Further investigations led authorities to the alleged suppliers of some of the chemicals as well as more contaminated wine near Masafra in Italy's southern Puglia province.

Authorities now suspect that a criminal network possibly controlled by the mafia was involved in producing the potentially toxic wine and arranging its distribution.

The separate investigation on false labels is centred in Tuscany where bottles labelled as high quality Brunello di Montalcino which is made exclusively from Sangiovese grapes, in fact contained blends of other vintages.

Prosecutors in Siena have placed 14 people under investigations, but several well known producers implicated mentioned in the Espresso report including Antinori, Banfi, Frescobaldi and Argiano have denied any wrongdoing.

"It is scandalous that the media is combining the case involving the Brunello di Montalcino with the other cases," Tuscany's top regional agriculture official Susanna Cenni was quoted saying by the ANSA news agency.

Cenni made the remarks at Vinitaly, Italy's largest annual wine fair which opened on Thursday in Verona. (dpa)