Major Japanese mobile phone carrier KDDI has revealed that it is managing some of the data on its customers on a server in Hong Kong through a US company.
KDDI has outsourced operations needed for data communication services abroad to the US firm.
KDDI says the US firm stores data on customers' phone numbers when billing them for the use of their mobile phones while abroad and the number of packets on servers in Hong Kong and Singapore.
The Japanese carrier said that data does not include information that could identify users, and that important data on customers is stored within Japan.
But in light of the political situation in Hong Kong, KDDI says it will consider moving the data in the Chinese territory to other countries, including Japan.
In a recent revelation, the personal data of users in Japan of popular messaging app Line was found to be accessible from mainland China.
The company operating Line has since acted to block any access from China.