Italy has started an investigation into Google Inc's Street View web service, a local watchdog said on Wednesday following the U.S. group's announcement it had accidentally collected personal data over wireless networks.

Google said last week its fleets of cars which have been photographing streets around the world had for several years accidentally collected personal information -- which a security expert said could include e-mail messages and passwords.

Italy's privacy regulator said it would verify whether Google treated correctly the data acquired by Street View, which allows users to navigate around a 360-degree view of city streets using pictures taken by Google's camera vehicles.

The regulator said Google Italy had admitted it collected pictures but also data regarding the presence of wireless networks ... as well as electronic communications, eventually transmitted by users via unprotected wireless networks.

Asked for comment, a Google Italy spokeswoman referred to Friday's statement that Google was approaching regulators in the affected countries about how to dispose of the data, which Google said it never used.

(Reporting by Danilo Masoni; Editing by David Holmes)