Ibrahim bin Hashim, from Al-Husayn bin Sa'id, from Ali, from Imam Abu Ibrahim عليه السلام:
I asked Imam عليه السلام about a deceased person who dies while in a state of major ritual impurity (janabah). Imam عليه السلام said: "One washing (ghusl e mayyat) is sufficient."
Ali Akbar al-Ghaffari
Tahdhīb al-Aḥkām fī Sharḥ al-Muqniʿah, vol. 1, p. 457