Unit Ei 1644 — also known as Unit 1644, Detachment Ei 1644, Detachment Ei, Detachment Tama, The Nanking Detachment, or simply Unit Ei, was a Japanese laboratory and biological warfare facility under control of the Epidemic Prevention and Water Purification Department. It was established in 1939 in Japanese-occupied Nanjing as a satellite unit of Unit 731. It had 12 branches and employed about 1,500 men.