Google's offices in Seoul were raided Tuesday by the Korean National Police Agency.
"[We] have been investigating Google Korea on suspicion of unauthorized collection and storage of data on unspecified internet users from Wi-Fi networks," police said in a statement reprinted widely in the media.
The data collection was related to the upcoming launch of Google's Street View service in South Korea, police said.
Google said Tuesday in a statement that police visited Google Korea "in conjunction with their investigation around data collection by Street View cars."
It added: "We will co-operate with the investigation and answer any questions they have."
In a blog post on May 14, Google acknowledged that its Street View vehicles mistakenly gathered private information from Wi-Fi networks that were not password-protected while collecting photos for the mapping service. However, it said it never used the data in Google products.
The company said it shut down its cars and contacted regulators in affected countries to ask how to dispose of the data once it became aware of the problem.
Nevertheless, privacy watchdogs in several countries, including Canada, have since announced investigations into the privacy breach.