Gmail users were sent a security alert on Monday, advising them that an unknown device had checked into their account.
But the alerts were sent by mistake, according to Mashable.
Google notified users about the gaffe with a message in its Admin Panel, an area apparently limited to G Suite clients, and advised them to change their passwords. It is now investigating the incident, and is eyeing a possible cause, most likely an internal error.
The exact number of people alerted wasn’t known at deadline.
New sign-in notifications are sent when someone has successfully logged into an account via another device.
Google states in a general information area: “If you suspect yourGmail account may have been hacked, there's a quick and easy way to get an activity log. Gmail can also be set to send you an alert whenever there's unusual activity.”