Google's Seoul office was raided on Tuesday on suspicion the Internet search firm's mobile advertising unit AdMob had illegally collected data, South Korean police said, the latest setback to Google's Korean operations.
The probe into suspected collection of data on where a user is located without consent highlights growing concerns about possible misuse of private information as more people use mobile devices such as smartphones and tablets.
Last month, Apple defended its use of iPhone location data, but denied that it was tracking the movements of customers, while consumer electronics giant Sony is grappling with a massive data breach.
"We suspect AdMob collected personal location information without consent or approval from the Korean Communication Commission," a South Korean police official said.
A Google spokesman confirmed that the police had visited its Seoul office and told Reuters the company was cooperating with their investigation.
The probe comes as the U.S. Federal Trade Commission is considering a broad investigation into Google and reportedly alerting high-tech firms to gather data ahead of a probe of Google's dominance of the Internet search industry.
Google and Apple have been targeted by U.S. lawmakers over their protection and use of consumer data from mobile phone applications of personal data such as where users are located.
Google executives have talked about the ability to target advertising to users based on location.
Google has already been the subject of a series of probes in South Korea and the United States over data collected by its controversial fleet of "Street View" cars since last year.
South Korea's top Internet portals filed a complaint with anti-trust regulators last month claiming Google was unfairly stifling competition in the mobile Internet search market of one of the world's most wired countries.
Google is a stellar performer in the booming smartphone and tablet market, as device makers are increasingly adopting its free Android operating platform to counter heavyweight Apple.
Global technology firms including Microsoft are trying to rein Google's growth.
The global smartphone market is forecast to grow 58 percent this year and Android will account for 39 percent of the market, according to research firm Gartner.
In the tablet market, Apple's share will gradually decline to 47 percent by 2015 from 69 percent this year, with Google's share forecast to rise to 39 percent from 20 percent now, Gartner said.
(Additional reporting by Miyoung Kim and Jonathan Hopfner in SEOUL and Kenneth Li in NEW YORK; Editing by Dhara Ranasinghe)