The once-in-a-generation winter storm in Texas that knocked out the state’s power grid in February may have killed as much as five times as many people as the state has confirmed in its official death toll. The state has reported 151 deaths connected to the storm—but a BuzzFeed News analysis of excess deaths in Texas right before and after the storm shows that around 700 people died in the week of the most widespread power failures. Beto O’Rourke, the one-time Democratic presidential hopeful, cited the BuzzFeed News analysis in a tweet that read: “We now know that the Texas government’s repeated failure to modernize our energy systems killed over 700 Texans in February’s winter storm.” The analysis reportedly shows that there were between 426 and 978 excess deaths in Texas in the week ending Feb. 20. Texas Gov. Greg Abbott’s press secretary told the site that he mourns “every single life lost” during the storm, but did not answer questions about the massive difference in the numbers. Many of the official deaths that have been counted were due to hypothermia, according to state reports.