Ofqual has said it is "working closely" with awarding organisations and the Department for Education to prepare for potential exam disruption in the event of a major coronavirus outbreak.
The regulator told Tes that trying to "put a label" on the situation is difficult as "so much as happened so fast", but the smooth running of exams could be affected if a percentage of pupils are not able to sit the tests.
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In the meantime, Ofqual said schools and colleges should continue to prepare for summer exams and assessments as normal.
A spokesperson said: "Some of the questions [about if exams will go ahead] are: would children be available; would students be there; what if a percentage of students are and are not?
"The situation with this is so changeable, and so much has happened so fast, so trying to put a label on it at the moment is really quite difficult, but those discussions will continue.
The spokesperson advised schools to "keep a close eye on the website" to ensure they can react to any updated guidance on the evolving risk from the virus.
In a separate statement on the government website, Ofqual added: "We are working closely with awarding organisations and the Department for Education to consider how to manage any particular risks to the smooth running of exams and assessments should there be a widespread outbreak of coronavirus.
"We will update our existing guidance to reflect any specific arrangements schools and colleges should put in place if required.
"In the meantime, students, schools and colleges should continue to prepare for the summer exams and assessments as usual."