County officials on Wednesday unveiled a new partnership for an app that would help residents discover if they’ve been exposed to someone known to have COVID-19.

The app, called Citizen, is already widely used as it sends users location-based alerts in real-time. Users can opt into “SafePass” or the contact tracing feature that uses Bluetooth to track when users have been in contact with each other. When a resident is tested and inputs their positive results, the app notifies their contacts anonymously.

Officials called it a “valuable tool” in contact tracing efforts, but noted that traditional contact tracing will still be used as well.

“For contact tracing to be effective, contacts need to be traced and notified immediately,” so people can quickly quarantine and get tested, said county supervisor Kathryn Barger.

The app’s founder, Andrew Frame, gave an example of the app in use from when the feature was still being tested: a woman turned it on before going to a protest and two days later she was alerted that she was exposed just before going to visit her immunocompromised parents, so she went to get tested before visiting them. The app can also tell a person where and when they were potentially exposed.

Long Beach Mayor Robert Garcia encouraged residents to download the app “to do something today to help fight COVID-19.”

The data is encrypted and anonymous with additional privacy precautions to protect users, officials said.

“This is a way to cover more ground and cover it quickly,” said Los Angeles Mayor Eric Garcetti.

Garcetti also announced the opening of a mobile testing kiosk at Union Station, which will test up to 500 people per day, Wednesdays through Sundays from 9 a.m. to 3 p.m. with or without appointments.