Chinese media lists the names that were called to the training camp between April 1 and June 30. And that list includes Sun's name.
China's swimming association rejects the allegations of calling the suspended Sun to the camp, saying in a brief statement that the list was incorrect.
However, it does not soothe the international anti-doping organization Wada, which in a message to the news agency AFP says to sort out the incident.
The 28-year-old Sun, who has a world record of 1,500 meters freestyle, got a long suspension because he had a previous suspension for taking a banned substance. That event, in 2014, gave only three months of suspension.
When the doping tests knocked on his home in September 2018, Sun refused to submit blood and urine tests, and in addition, he broke a blood test with a hammer. It eventually gave Sun Yang the eight-year suspension.