Peter Sagan soloed to victory in the Giro d'Italia's 10th stage on Tuesday after two teams, Mitchelton and Jumbo-Visma, were forced to pull out before the stage because of positive COVID-19 tests.

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Sagan, riding for Bora, ended his winless drought going back to the 2019 Tour de France, as Portugal's Joao Almeida kept the leader's pink jersey in the race scheduled to finish in Milan on October 25.

"I won with my style, putting on a show!" said 30-year-old Sagan.

"We were in the breakaway all day, I had good legs, and went solo on the uphill before descending with care in the downhill and then full gas in the final kilometers."

Mitchelton pulled out before the start of the 177km stage because of four positive tests, and Jumbo followed after Dutch contender Steven Kruijswijk tested positive.

Kruijswijk, who finished third in the 2019 Tour de France, returned a positive test along with Sunweb's Australian Michael Matthews.

"We are trying to keep the situation under control," said Giro race director Mauro Vegni.

"This morning, all the teams that have had positive cases have undergone new quick tests and we will do the same the day after tomorrow. So far we have done almost 1,500 tests and it is impossible to do more."

Sagan, one of the most successful riders in the peloton with three world titles, achieved his first success in the Giro, to complete his set of stage wins on the three big tours -- France, Italy, Spain.

The Slovak attacked several times in the mountainous last 60km, finally breaking clear uphill 12km from the finish line to cross alone 19sec ahead of American Brandon McNulty with Almeida third at 23sec.

Danish Jakob Fuglsang was the day's biggest loser after suffering a puncture 10km from the finish and losing a minute on his rivals.

The peloton was reduced to 145 riders from the 176 who started the race in Sicily on October 3.

The Mitchelton team said they had been notified of four positive results for "staff members" after tests conducted on Sunday.

"Upon receiving the results, Mitchelton-Scott immediately withdrew its team from the race and will focus on the health of its riders and staff and their safe movement to areas of quarantine," the team said.

'I just feel fit'

Mitchelton general manager Brent Copeland added: "As a social responsibility to our riders and staff, the peloton and the race organization we have made the clear decision to withdraw from the Giro Alitalia."

Copeland said those who tested positive "remain asymptomatic or with mild symptoms" and would undergo a period of quarantine.

Mitchelton had already been hit by Saturday's withdrawal of Briton Simon Yates, their lead rider, who became the first rider to test positive for Covid-19 at a Grand Tour.

Yates, who was 21st in the standings ahead of Saturday's stage with overall victory still potentially within his grasp, tested positive for coronavirus after developing a mild fever on Friday.

The announcement of Jumbo's complete withdrawal followed was another blow for Kruijswijk, a top-five finisher in all three Grand Tours who missed this year's Tour de France with a knee injury.

"Within the team, we take a lot of measures to avoid contamination," said the 33-year-old Dutchman, who showed no virus symptoms.

"I just feel fit. I can't believe I got it. It is a very big disappointment to get this news. It is a pity that I have to leave the Giro this way."

And Team Sunweb added that the now-quarantined Matthews was "asymptomatic, feels healthy".

The positive tests throw into doubt the future of the three-week Giro, which now has 21 teams, with nearly two weeks to run.

Although Tour de France director Christian Prudhomme and four staff members from four different teams tested positive, last month's Grande Boucle finished without any riders failing tests.