At least 9,311 Russian soldiers have died since Russia launched its invasion of Ukraine nine months ago, according to an independent investigation conducted jointly by the BBC Russian Service and independent Russian news outlet MediaZona. The death toll, which was published by the BBC on Friday, only includes officially confirmed fatalities, meaning that the true number of Russia’s losses in the conflict to date could be as much as twice that number, the U.K.

public broadcaster said. The number of Russia’s irreversible losses, a figure that includes the severely injured and the missing, could be as high as 100,000 people, the BBC said.Among those included in the count by the BBC are 326 men called up during Russia’s recent mobilization drive.

At least 35 of them died before they could be deployed to the frontlines “most often due to heart problems, accidents or alcohol abuse,” the report said.The Russian army reportedly sustained particularly heavy losses among its top echelons.

Army officers make up over 15% of the overall death toll, while the count also includes four generals, 47 colonels and 101 military pilots. Infantry and airborne forces sustained the highest number of losses since the beginning of the war, closely followed by so-called volunteer battalions — regional militias made up of civilian volunteers — which have collectively lost as many as 1,050 servicemen.  The investigation showed that the largest number of dead servicemen came from southern Russia’s Krasnodar region, followed by the Siberian republic of Buryatia and the North Caucasus republic of Dagestan.By contrast, Moscow, which is home to nearly 9% of the country’s population, has lost just 50 residents in the war, or just 0.5% of the total.