Belgium became Thursday the latest European country to investigate Google's Street View picture map after cars taking pictures for the programme collected private data.
"We have received a complaint from the privacy protection committee and we have opened an investigation," federal prosecutor's spokesman Eric Van der Sijpt told AFP.
A commission official told the Flemish newspaper De Morgen that the body believes the US Internet giant committed a "flagrant violation of privacy protection laws."
With cameras mounted on their roofs, Street View cars take 360-degree pictures of locations that are then posted to Google Maps, offering users panoramic views of roads.
Launched in 2007, Street View has sparked privacy concerns in several European countries including France, Germany, the Netherlands and Switzerland.
In May, Google admitted that its Street View cars, taking photographs of cities in more than 30 countries, had inadvertently gathered data sent over unsecured wifi systems, sparking complaints by data regulators worldwide.
Google Belgium apologised on Thursday.
"We are sorry to have unintentionally collected data from unsecured wifi networks," Google said. "As soon as we realised what happened, we interrupted the activities of our Street View cars and we informed the authorities."
"We neither looked at nor used the data for Google products or services. We are in contact with Belgian authorities and will continue to answer all of their questions."
Last month, France's data privacy regulator imposed a record fine of 100,000 euros ($142,000) on Google for collecting private information while compiling photos for Street View.
Earlier this month, a Swiss court ordered Google to make all images of individuals and vehicle plates unrecognisable on Street View.
Explore further: France fines Google 100,000 euros over Street View (Update)