England have returned two "unconfirmed" positive coronavirus tests after the abandonment of their first one-dayer against South Africa.
Sunday's game in Paarl had been called off 30 minutes before it was due to begin, with two members of staff at the team hotel having tested positive for COVID-19.
A decision will be made on whether the final two matches of the series will be played on Monday and Wednesday as scheduled once the results of the tests have been ratified.
England had previously expressed concern over the strength of the bio-secure environment.
"We regret that we are unable to play in today's ODI, but the welfare of the players and support staff is our primary concern and whilst we await the results of further tests the medical advice from both teams was that this game should not take place," says Ashley Giles, managing director, England Men's Cricket.
"We remain in constant dialogue with Cricket South Africa and will continue to work closely with them to determine how best to move forward."
South Africa's director of cricket Graeme Smith said they hope the final two matches could be played.
"We are deeply regretful of the situation we find ourselves in after the amount of time and energy that has been put in place to host a successful tour," he says.
"We are in continuous talks with the ECB as we navigate the situation under the guidance of our combined medical teams."
The unconfirmed positive results take to seven the number of COVID-19 related incidents on the six-match white-ball tour, two of which occurred in the South Africa camp before the series started. There have now been five in the bio-secure environment.
Roy Davies, general manager of the Vineyard Hotel where the teams are staying, said the hotel is still investigating how two staff members contracted the virus.
"At this stage, it is not clear how the staff members became infected as neither have left the biosecure area since 16 November and they do not work on the same team or in the same area," he said in a statement.
"Our COVID-19 response team is endeavouring to establish all the facts and contact tracing is underway."
It would be a huge blow for cash-strapped Cricket South Africa if the rest of the tour were to be cancelled and place into doubt future visits by Sri Lanka, Pakistan and Australia in the next few months.