The coronavirus outbreak in Glasgow is a result of 'significant community transmission' that could be linked to international travel.
Health Secretary Humza Yousaf said urgent work is currently ongoing to understand the outbreak in the south side of the city and how the Indian variant arrived in the community.
His comments come after it was announced that Glasgow City would remain under Level 3 restrictions for another week.
Nicola Sturgeon confirmed on Friday that cases have continued to rise in the city over the last week by around 30 per cent - from 112 per hundred thousand of the population to 146. Test positivity is now around 4.4% in comparison to 2.6% in Scotland.
The National Incident Management Team believes that the escalation of public health measures, including drop-in vaccination centres and mass testing, in Glasgow is stabilising and might be starting to improve the situation.
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Mr Yousaf told BBC Radio 4's Today: "In a few concentrated hotspots... we are seeing significant community transmission.
"The levels and the numbers of cases are continuing to rise."
In other parts of the country "local health teams tell us they are relatively contained outbreaks" linked to either schools or domestic clusters, but that was not the case in Glasgow.
"What we are seeing is it's coming in areas where there is a large, diverse community so therefore there is a probability the variant has come in from international travel.
"Therefore we are trying to get to the bottom of how it managed to get in."
