Nakazato's case is the ninth to emerge from the national federation since the COVID-19 outbreak began.

"It has been found that the federation's managing director Soya Nakazato has been infected with the new coronavirus," an All Japan Judo Federation statement read.

"Nakazato showed fever symptoms on March 5 and had undergone a PCR test on March 8, but was confirmed to be positive today.

"The Federation will continue to strive to prevent the spread of the new coronavirus by taking measures such as continuing to refrain from unnecessary emergencies.

"We apologise for any inconvenience this may cause, and we look forward to your continued support and encouragement in judo."

Eight other members of the All Japan Judo Federation have tested positive for coronavirus since April 4, prior to Nakazato becoming infected.

Nakazato has acknowledged the high number of cases within the federation after his positive test.

"We are extremely inconvenienced about the outbreaks in this federation," he said.

"Earlier, I was notified by a health centre near my residence that my test was positive.

"For the time being, I would like to concentrate on the treatment and try to recover."

All Japan Judo Federation President Yasuhiro Yamashita, an Olympic judo gold medallist, said the organisation's staff did not have close contact with the first infected person, or their family members, before April 1.

The statement suggested other individuals may have been infected during work or outside work hours by another person, with several employees reporting fevers until April 3.

The official said that with an incubation period of two weeks, it was difficult to determine the identity of people who were infected at the time.

Yamashita said the organisation had taken measures to prevent the spread of infection at an earlier stage, but that the federation "regret that this result was inadequate in terms of operation".

He expressed hope the number of cases will fall due to reduced contact between people, promotion of hygiene measures and refraining from unnecessary travel.

"We would also like to express our deepest gratitude to healthcare professionals and other people who are working hard to prevent the spread of infection," Yamashita, who is also the President of the Japanese Olympic Committee and an International Olympic Committee member, said.

"The Federation intended to take measures to prevent infection, but an outbreak occurred at the secretariat as in this case.

"The new coronavirus can potentially infect anyone, but by acting with strong awareness that each person will prevent the spread of infection, the risk of infection can be minimised.

"Protecting yourself protects your family and loved ones, and protects society as a whole. 

"It is a difficult situation now, but we believe that if everyone works together, we can overcome this difficulty.

"Again, we apologise for the great concern and inconvenience caused by the outbreak of the new coronavirus at the Secretariat of the Federation."

More than 1.8 million coronavirus cases have been confirmed worldwide, resulting in more than 114,000 deaths to date.

Japan has reported more than 7,000 cases and more than 120 deaths since the outbreak began.

The pandemic ultimately forced the postponement of the Tokyo 2020 Olympic and Paralympic Games to 2021.