Which of the following cause of death would cause an elevated level of cyanide?

During smoke inhalation in thermal deaths apa from CO, the other factors which contribute to death are oxygen deprivation, cyanide, free radicals (inactive surfactants, thus preventing oxygen from crossing the alveoli into the blood), and non-specific toxic substances. Ref: The Essentials of Forensic Medicine and Toxicology by Narayan Reddy, 27th edition, Page 285.