That mark topped his 46.80 swum at the February world championships in Doha.

“It was a magical moment, really magical,” Pan said. “The record was not just for the Chinese team, but for the world. This is a small step by breaking this record.”

In perhaps the most ferocious race in swimming, the 19-year-old Pan edged Kyle Chalmers of Australia, who clocked a 47.48 for silver and Romanian bronze medalist David Popovici in 47.49.

No world marks had been broken through the first four days in the pool at the Paris Games.

Chalmers won gold in the 100 free in the 2016 Rio de Janeiro Games, and was the silver medalist three years ago in Tokyo behind American Caeleb Dressel. Dressel did not qualify this time.

Pan has not been implicated in any of the doping allegations that have surrounded the Chinese swimming team in the run-up to the Olympics.

Chinese swimmers in Paris have pushed back strongly against those accusations and say they have been tested more frequently in recent months, sometimes three or four times a week.

Pan was asked about the testing and said it all seemed routine to him.

“This was standard,” he said. "The tests were done under all the regulations. I don't think it influenced my performance.”

WADA, the World Anti-Doping Agency, put out a statement on Tuesday in response to food contamination scenarios being used to clear athletes who test positive.

“WADA is generally concerned about the number of cases that are being closed without sanction when it is not possible to challenge the contamination theory,” the statement said.

“There have been many cases of positive tests that were eventually closed without sanction as no-fault violations, sometimes with unusual methods of contamination.”

WADA said it was also concerned about similar cases in the United States.