Issues causing random shutdowns in the iPhone 6s may affect more customers than initially believed.

While Apple has acknowledged that a select number iPhone 6s units built within a specific timeframe could experience issues with random shutdowns, the company is now saying that random shutdowns are affecting a wider pool of the devices. On a support page on its Chinese website, Apple says that it will issue a software update with diagnostic tools to help customers discover if their phone is affected by the issue.

From Apple:

A small number of customers outside of the affected range have also reported an unexpected shutdown. Some of these shutdowns can occur under normal conditions in order for the iPhone to protect its electronics. In an effort to gather more information, we are including additional diagnostic capability in an iOS software update which will be available next week. This will allow us to gather information over the coming weeks which may potentially help us improve the algorithms used to manage battery performance and shutdown. If such improvements can be made, they will be delivered in future software updates.

The random shutdown issue initially seemed to affect only those iPhone 6s models within a certain serial number range that were manufactured between September and October 2015. The company has launched a repair program to correct the issue for affected customers.