Beuran Hendricks and Keegan Petersen have been withdrawn from South Africa's Test squad to play Sri Lanka.

Neither player entered the tour bubble when the playing group convened on Saturday, after two positive Covid-19 results were detected last week. CSA cannot, for reasons of doctor-patient confidentiality, name who the infected players are.

The other 17 squad members have tested negative on all three occasions, thus making the environment bio-secure. South Africa will not add any players to the squad for the two-Test series which starts on Boxing Day.

Having cleared three rounds of testing, South Africa can begin training as a full squad on Wednesday after having staggered sessions so far. They will also no longer be confined to their hotel rooms at the Irene Country Club and can use communal areas, with social distancing rules in place, but will not come into contact with Sri Lanka, who are housed at the same venue. In addition, they will not be permitted to leave the venue except to travel to SuperSport Park and the Wanderers for the duration of the series.

Cricket South Africa have enforced stricter controls for this series than they did for the England tour - in which players were allowed to play golf at various courses around the Western Cape province - both at the behest of Sri Lanka Cricket and because the England tour was unsuccessful.

Three South African players tested positive for Covid-19 - one before the tour, one after entering the bubble and one after the T20 series - as did two hotel staff, and the one-day series was postponed. Two members of England's touring party also tested positive although, on verification, their results were confirmed as false positives. South Africa, who are also due to host Australia this summer, need the Sri Lanka series to take place without incident to get their international hosting back on track.

For that reason, they pushed the final round of domestic first-class matches, which were due to start last Sunday, into next year following positive cases in two of the three matches that began on December 13. Hendricks, Petersen and eight other players in the national squad were part of two of those games.

At SuperSport Park, the match between the Titans and the Dolphins was called off after the first day because a Dolphins' players tested positive while in Bloemfontein, the game between the Knights and the Lions continued despite a Lions' player testing positive on day three. Several more Dolphins and Lions players were also found to be infected.

The impact has been felt by the national squad who have lost at least one certain starter for the Sri Lanka Tests. Hendricks, who has only played one Test, would most likely have been the third seamer in the absence of the injured Kagiso Rabada. Hendricks debuted at the Wanderers last summer and took six wickets in the match, including 5 for 64 in the second innings, and is familiar with conditions up-country, having made the Lions his domestic home. Instead, South Africa will rely on Lungi Ngidi and Anrich Nortje for experience and could hand a debut to Glenton Stuurman, Migael Pretorius or Lutho Sipamla.

Petersen was less likely to play than Hendricks but, after three summers averaging over 50 domestically, he made a strong case to be considered at No.3. He should also have been the next man in line after being a non-playing member of the squad last season but will have to make way for one of Sarel Erwee, Raynard van Tonder or Kyle Verreynne for now.

Updated squad: Quinton de Kock, Temba Bavuma, Aiden Markram, Faf du Plessis, Dean Elgar, Keshav Maharaj, Lungi Ngidi, Rassie van der Dussen, Anrich Nortje, Glenton Stuurman, Sarel Erwee, Wiaan Mulder, Kyle Verreynne, Migael Pretorius, Dwaine Pretorius, Lutho Sipamla, Raynard van Tonder

Firdose Moonda is ESPNcricinfo's South Africa correspondent