A 32-year-old woman is found dead in a locked room with a kerosene stove burning nearby. The body shows extensive charring of the skin with a dark brown-black appearance, muscle contraction causing flexion of limbs (pugilistic attitude), and blistering of the skin. On autopsy, the lungs show bright pink discoloration and the trachea contains soot and carbonaceous material. Which finding is most indicative that the burns occurred ante-mortem?