California’s deadliest avalanche killed at least eight people in a ski group near Lake Tahoe on Tuesday. The six survivors used the iPhone’s emergency SOS feature to help first responders find them as they waited under a tarp and discovered some of the bodies, according to the Nevada county sheriff. Apple’s feature, introduced in 2022, allows users to text law enforcement, even if there’s no cell service or wifi by connecting the phone to a satellite.

First responders reached the skiers’ location and learned of the six survivors based on conversations held through the feature, Sheriff Shannan Moon said at a press conference on Wednesday.

California office of emergency services law enforcement chief Don O’Keefe said his staff spoke with one of the stranded guides for more than four hours to relay information to the sheriff’s office, which was leading rescue efforts. O’Keefe’s agency said in an emailed statement that this communication occurred through a personal locator beacon that had the ability to text; these compact devices also tap into satellite signals to allow communication in an emergency.

Law enforcement reported that a ninth person from the group of 15 is still missing, though presumed dead. Three were instructors with Blackbird Mountain Guides, and six were clients.

The iPhone’s emergency SOS feature is free for two years after purchasing an iPhone 14 or any later model and activating it. If a call to emergency services doesn’t go through, the smartphone links with a satellite and allows users to text relevant agencies. Onscreen instructions can guide a user on how to connect. Apple notes that users will have a better chance of doing so if they are “outside with a clear view of the sky and horizon”. Once connected, the iPhone shares key information with emergency responders, including Medical ID and emergency contact if that information is added before losing service, as well as location, including elevation and remaining battery life.

This isn’t the first time Apple’s emergency SOS feature has helped users in crisis. The tech has reportedly been used to help law enforcement rescue a man who suffered a serious ankle injury in a California forest, stranded hikers in Oregon and Colorado and two people who were in a car crash in Canada.