He noted impurities found by the Japanese police were usual byproducts in methamidophos and couldn't prove the source of the substance.

The conclusions of Chinese and Japanese police were different but both based on their own evidence, said Yu, urging the two countries to further cooperate in investigations until the truth comes out.

"I didn't mean the crime must have been committed in Japan," he told reporters.

Meanwhile, Wei said the ongoing investigation can't eliminate the possibility of the pesticide being obtained from other countries and then brought to Japan. He stressed investigators should be open to all possibilities.

Chinese police caught an unidentified number of Japanese journalists trying to carry methamidophos they illegally purchased in Hebei out of the province on February 15, Wei said. He didn't specify their identity or other details.

China banned the use of methamidophos in agricultural production in 2007 and has made it illegal to produce, sell, carry and transport the substance since the beginning of 2008.

(Xinhua News Agency February 28, 2008)