In all, seven olive oil plants were closed and about 40 people were arrested for allegedly adding sunflower and soybean oil to olive oil and selling it as extra-virgin olive oil in Italy and abroad, ANSA reported.

''The Italian food police are doing a great job but where are the local food authorities that should be checking these products?'' said consumer rights group ADUC chief Primo Mastrantoni.

Franco Verracina, chief of the farm association Copagri, said he hoped the case would not hurt legitimate producers.

'We can't allow the 100 percent of true producers that raise Italy's image in the world to be hurt by media hype that is not justified because policing has been shown to be constant, prompt, efficient and transparent,'' Verracina said.

Italy is the European Union's second-biggest producer of olive oil behind Spain, the news service reported.