Sitel call centre in Bellshill have now been confirmed by Tuesday evening - 15 staff members and five people with connections to the call centre.
One extra case has been confirmed since yesterday.The cluster has sparked concerns, with some workers at the Maxim Park site claiming managers shut the blinds after police came to investigate claims of safety breaches.
Labour MSP Monica Lennon referred the call centre to Police Scotland after being inundated with complaints about Sitel at the height of the pandemic.
But now the NHS board has moved to address public health concerns, saying those who visited any of the locations linked to the outbreak do not have to isolate if they do not have symptoms.