The Italian cartel office has opened an investigation against Google on suspicion of abuse of market power with regard to online advertising, the agency says.
The company's offices in the country had been inspected together with the financial police on Tuesday, it said in a statement.
According to the cartel office, Google is suspected of having violated EU rules on abuse of a dominant market position in its data collection practices in Italy, which may have weakened competition and affected consumer interests.
The case concerns the decryption of ID data and the collection of data about people who look at online articles and the advertising placed around them.
The authority will investigate whether Google is abusing its technical capabilities and size, estimating that the company's online advertising revenue in Italy in 2019 will exceed 3.3 billion euros ($A5.5 billion).
By means of cookies, which store data, advertisers, agencies and advertising brokers could collect important information concerning the consumer decisions of users, the authority explained.
This information could then be used to create personalised campaigns.
In addition to this data, Google has several tools that can be used to determine a user's interest profile.