California is rolling out a voluntary smartphone tool to alert people if they spent time near someone who tests positive for the coronavirus as cases and hospitalizations soar throughout the state.

Californians will be able to activate the tool in their iPhone settings or on Android phones by downloading the CA Notify app from the Google Play store. Many residents will get a notification Thursday inviting them to participate.

Officials say the tool doesn’t track people’s identities or locations but uses Bluetooth wireless signals to detect when two phones are within 6 feet of each other for at least 15 minutes.

The encounters are temporarily logged in a way that doesn’t reveal a person’s identity or geographic location.

“The process is private, anonymous and secure, and is one of the many tools in the state’s data-driven approach to help reduce the spread,” Newsom said in a statement.

If people who have activated the technology test positive for the virus, they get a verification code from the California Department of Public Health and can use that to send an anonymous alert to other participating phone users they might have exposed over the past 14 days.

The recent rise in infections began in October and is being blamed largely on people ignoring safety measures and socializing with others.

Sixteen other states, plus Guam and Washington, D.C., have already made available the system co-created by Apple and Google, though most residents of those places aren’t using it. The tool has been used on a pilot basis on University of California campuses.

This is a developing story and will be updated.