"This time is for real! Negative," said the 32-year-old Italian who intends to take part in her fifth and final Olympic Games in Tokyo next year.
Pellegrini, who had planned to compete in the International Swimming League in Budapest before she tested positive, could now compete in the final part of the event which runs until Nov. 22.
Pellegrini won gold in the 200 metres freestyle at the Beijing Olympics in 2008 and the world championship in the same event in 2009, 2011, 2017 and 2019, plus the world title in the 400 metres freestyle in 2009 and 2011. (Reporting by Brian Homewood, editing by Ed Osmond)