Wei Di, head of the Chinese Football Association, warned that Chinese footballers should be stay away from banned drugs.

Wei said that Chinese footballers should always pay attention to what they eat and all team doctors should be specially trained to avoid to provide wrong medicines.

"I believe that no one will take banned substances intentionally because in soccer these drugs can hardly enhance performances," he said. "But I am worried that these substances might be contained in food and other nutrition substances."

He added, "We must take enough precaution measures, otherwise it will be too late when somebody tests positive."