This means that all 166 cyclists who remain in the competition were allowed to start on today's stage, pancake plate 168 km between the islands Ile d'Oleron and Il de Re along the coast north of Bordeaux.
It was the third mass test conducted during this year's competition.
In the last two days, most during yesterday's rest day, 650 tests have been performed.
However, tour general Christian Prudhomme has tested positive.
He has now left the tour and the new race director François Lemarchand (from the Paris-Nice race) flagged off today's stage.
There is a strict health protocol and the participating stables are in "bubbles" without contact with the outside world.
If two people, both skiers and staff are included, in the same stable are tested positive within a week, it will be thrown out of the competition which has a finish in Paris on 20 September.
Next testing 14 September
The competition began two months late on August 29 to adapt to the corona pandemic that hit France hard with more than 30,000 deaths.
A fourth mass test will take place on September 14, which is the next rest day.
This is the first time ever that the Tour de France passes two islands on the same stage.
There are suitably enough bridges to both islands.
The full name of the resorts on today's stage is Ile d'Oleron Chateau-d Oleron and Ile de Re Saint-Martin-de Re.