Mobile carrier NTT Docomo said Wednesday that users who update its app, which currently enables users to track down lost phones, will thereby allow the carrier to provide location information to investigative authorities without informing them.

Earlier this month, NTT Docomo said five smartphone models, some of which are already on store shelves, will allow authorities to track down the location of its smartphones without informing users. But it is not clear how this will affect users already using NTT Docomo smartphones equipped with the Android operating system.

If the users of existing models update their NTT Docomo location service app, which has been available since May 19, it will allow the mobile carrier to provide information to investigative authorities with warrants without informing users.

NTT Docomo, however, stressed that it will not provide such information "unless there was a warrant or in cases of emergency in which users' lives are threatened," said the mobile carrier's spokesman on condition of anonymity, adding that it may be helpful, for example, in cases where the user is injured following a natural disaster.

The move came after the Ministry of Internal Affairs and Communications revised its privacy policy guidelines for carriers in June last year so that they will not be obliged to inform users when the government orders them to provide location information.

Since the ministry's guidelines urge mobile carriers to install such a function, other carriers are likely to follow suit, industry sources said. SoftBank Corp. and KDDI Corp., operator of au, have said a program to install the same service is still in the works.

NTT Docomo's privacy policy stipulates that it will offer users' location information to government organizations without notifying users if doing so will interfere with the investigation or other issues.