Some Nokia 7 Plus smartphones sent data to servers in China, according to Norwegian public broadcaster NRK.
Finland's HMD Global, which pays for the right to produce and market Nokia-branded phones, confirmed there was a software glitch on a batch of the handsets which has been corrected.
NRK reported on Thursday that personal data of some of the phones' owners had also been sent to Chinese servers, but HMD denied this.
The Norwegian public broadcaster was contacted by a Nokia 7 Plus owner who tracked the data sent from his handset. He told NRK that the phone had sent unencrypted data packets to a server in China as the phone was powered up, when the screen was activated or when the phone was locked.
Finland's data ombudsman Reijo Aarnio told news service STT that preliminary information he has seen indicates that Nokia phones had actually sent users' personal information to Chinese servers. The data was reportedly sent to servers run by state-owned China Telekom, China's third-largest mobile telecommunications provider.
Aarnio told news service Reuters that he plans to determine whether alleged breaches occurred that involved "personal information and if there was legal justification for it."
Telecommunications firm Nokia, which receives licensing fees from HMD, did not issue a statement on the matter, according to Reuters.
What was or wasn't sent?
NRK reported that the sent data packets included information about the phone's location, the nearest cell tower, its telephone number, the SIM card number and the phone's unique IMEI number.
Using a combination of this data would make it possible to track where the phone was located in real time.
HMD Global said the problem only affected one batch of the Nokia 7 Plus and caused those phones to send activation data to a server in China. HMD said the personal information of the phones' users could not be identified with the data that was sent.
The company said the issue has been fixed and that the remedy was part of a security update which was sent to all of the affected handsets.
The Nokia 7 Plus, which was released as a flagship handset last year, has been quite popular in China. The first quarter-million of the Android-run handsets reportedly sold out in the first five minutes they were put on the market.