Photo taken on July 28, 2015 shows relics excavated from the remains of Japan's notorious Unit 731 headquarters in Harbin, northeast China's Heilongjiang Province. Incineration pits and traces of explosives left by Japanese invaders destroying evidence have been found at the remains of Japan's notorious Unit 731 headquarters in Harbin. The new findings were part of an operation to destroy a bacteria lab and burn experimental facilities at the site. Unit 731 was a top-secret biological and chemical warfare research base established in Harbin in 1935 as the center of Japan's biological warfare in China and Southeast Asia during WWII. The retreating Japanese invaders blew up the base when the Soviet Union took Harbin in 1945.