The actual circumstances of Korolev's death remain somewhat uncertain. In December 1965, he was supposedly diagnosed with a bleeding polyp in his large intestine. He entered the hospital on 5 January 1966 for somewhat routine surgery, but died nine days later. It was stated by the government that he had what turned out to be a large, cancerous tumor in his abdomen, but Glushko later reported that he actually died due to a poorly performed operation for hemorrhoids. Another version states that the operation was going well and no one was predicting any complications. Suddenly, during the operation, Korolev started to bleed. Doctors tried to provide intubation to allow him to breathe freely, but his jaws, injured during his time in a Gulag, had not healed properly and impeded the installation of the breathing tube. Korolev died without regaining consciousness. According to Harford, Korolev's family confirmed the cancer story. His weak heart contributed to his death during surgery.