An expert has denied a report that a deserted toxic gas experiment site set up by the Japanese army during its Chinese invasion has been found in Northeast China.

"Yes, we have been there, but the site was empty and we haven't found any evidence to prove it is a toxic gas experiment site," Yang Yanjun, deputy director of the 731 Institute of Harbin Academy of Social Sciences told China Daily on Tuesday.

"Currently we have no plans for further investigations. But we will release the result as soon as we know anything for certain," Yang said.

A joint investigation team between China and Japan discovered the site in Mudanjiang city, Heilongjiang province, recently by comparing old maps left by the Japanese army and navigation maps. The Harbin Academy of Social Sciences was part of the investigation team.

An estimated two million chemical weapons were left by the Japanese invaders at the end of World War II in a dozen Chinese cities, Bu Ping, vice-president of the Heilongjiang Academy of Social Sciences and a researcher of chemical weapons told Xinhua News Agency.

One person was killed and 43 injured when barrels of mustard gas abandoned by Japanese forces started to leak when they were dug up at a construction site in Qiqihar, Heilongjiang province in 2003.