Thousands of people were killed by Hurricane Maria, which blasted Puerto Rico on Sept. 20, 2017 with devastating results. But the Puerto Rican government has only publicly identified 64 victims. In the weeks and months after the hurricane, reporters from Quartz, Puerto Rico’s Center for Investigative Journalism, and the Associated Press set out to find the victims left out of the official death toll. We found 487—the most extensive record yet of who died and why because of Maria. Here is how our count compares to the government’s: Identifying natural disaster victims is not only important to provide closure for grieving family members. It also gives government officials a more detailed picture of how a disaster is unfolding on the ground—and how to better handle it. Victim relatives we interviewed linked each of the deaths to Hurricane Maria and the island’s damaged infrastructure. But Puerto Rico’s government never did, missing out on key information it might have used to prevent further deaths. We found that people were dying from the same preventable causes months after Maria hit. Patients with treatable ailments like bedsores and kidney problems couldn’t get medical attention. The lack of power continued to cause accidents: one victim was run over by a car because traffic lights were still out in January 2018, more than three months after the hurricane. Puerto Rico’s government has acknowledged that many more people died than it originally counted. It has changed its official toll to 2,975, based on a study it commissioned from George Washington University. But that’s a statistical estimate, calculated by comparing all post-Maria deaths in Puerto Rico to mortality in previous years. It doesn’t show what caused the deaths. The stories from victims’ relatives do. They offer key details that can help Puerto Rico and other places prepare for future catastrophic storms, say experts. “Accurate death tolls matter because they save lives,” says Mario Marazzi, director of Puerto Rico’s Statistics Institute. Explore the victim database created by Quartz, CPI, and the AP in English and Spanish here. Quartz News is a weekly video series bringing you in-depth reporting from around the world. Each episode investigates one story, breaking down the often unseen economic and technological forces shaping our future. Click here for previous stories.