According to a widely-accepted theory, Choei coaxed a prison worker named Eizo who belonged to hinin (one group comprising the lowest rank of Japan's Edo-period caste system, often ex-convicts or vagrants) into setting fire to the place.
この火災は、長英が牢で働いていた非人栄蔵をそそのかして放火させたとの説が有力である。