China plans to investigate an allegation that 99 percent of the materials that make up illegal substances come from China, but remains doubtful about the World Anti-Doping Agency's statistics, a Chinese official said on Tuesday.

China's move came as a result of a striking comment from WADA Director-General David Howman, who told reporters during a WADA media symposium in London that "99 percent of the raw materials that are used through the Internet to make up (drugs) in your kitchen or your backyard laboratory are emanating from China".

Howman's remarks immediately drew great attention from the State General Administration of Sport, the government organization that runs sports in China and provides financial support for the country's anti-doping drive.

"We are shocked at Mr Howman's comment," said China's anti-doping chief, Jiang Zhixue.

"We are wondering where this 99 percent (figure) came from and what is his evidence. We have asked for a more detailed explanation from WADA."

Meanwhile, Jiang admitted problems in China's anti-doping fight.

"There are problems, such as the illegal sale of banned drugs through the Internet. So, we have decided to launch an investigation into WADA's allegation," he said.

Jiang said the probe needs to be a coordinated effort between multiple governmental departments, like the action taken ahead of the 2008 Beijing Olympic Games, when a number of workshops that illegally produced materials were shut down and supervision and control of drug sales were stepped up.