The entire South African rugby squad is in isolation after three players tested positive for coronavirus ahead of the British and Irish Lions tour.
Sunday's planned training session in Johannesburg was cancelled as a result of the COVID-19 cases.
SA Rugby, which governs the national team, has said that "a decision on further team activities will be made shortly".
The development throws into doubt the viability of their warm-up Test against Georgia on Friday night.
The Lions, a team selected from players eligible to represent England, Ireland, Scotland or Wales, fly to Johannesburg from Edinburgh on Sunday night, with their opening tour match taking place in the city on Saturday 3 July.
In a statement, SA Rugby said: "The Springboks cancelled Sunday's planned training session in Johannesburg as a precautionary measure when scheduled testing protocols returned three positive COVID-19 test results when the team assembled on Saturday.
"Three players tested positive for the virus following stringent real-time polymerase chain reaction (PCR) testing procedures on arrival at the team base.
"Team management immediately put the squad into self-isolation as a precaution until specialist medical advice is sought from the Castle Lager Lions Series Medical Advisory Group (MAG).
"A decision on further team activities will be made shortly. SA Rugby director of rugby Rassie Erasmus emphasised that the team had followed all the necessary precautions since the start of the three-week conditioning camp hosted in Bloemfontein, which included mandatory COVID-19 testing three times a week, and that they would be led by specialist advice before any action is taken."
The tour has endured a weekend to forget, with the Lions losing captain Alun Wyn Jones and flanker Justin Tipuric to injuries during Saturday's 28-10 victory over Japan at Murrayfield.
Ireland scrum-half Conor Murray has replaced Jones as captain, while Wales forwards Adam Beard and Josh Navidi were summoned to join the squad.
The three-Test series between the Lions and world champion Springboks kicks off in Cape Town on 24 July.
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