A further maths A-level paper due to be sat by around 7,000 students on Thursday has been replaced following the leak of an earlier exam.
A cheating probe was launched last week after images of an Edexcel maths exam were circulated online.
But Pearson, the exam board’s parent company, has decided to replace the forthcoming paper due to the actions of the unnamed centre concerned being investigated.
It said the probe revealed that a package containing the further maths paper had been opened by an individual at the centre.
According to Pearson, there is no evidence to suggest that the withdrawn test or any of its questions have been leaked, but it is taking “precautionary steps” to safeguard the exam for the students.
Sharon Hague, senior vice president, schools at Pearson, said: “We have reached out to all of our centres directly to inform them of this decision.
“We will continue to support and communicate with them through this unusual yet necessary step, that is vital for the safeguarding of confidence in the examination system and to ensure fairness for all learners.
“Our message to students is not to worry about this and focus on your revision as you normally would.”
Arrangements are being made to deliver the papers to all centres shortly before the exam, apart from the one being investigated.
There, separate arrangements are being made to ensure its students can complete their exams.
In a video message to students, teachers and parents, Ms Hague said it is necessary for everyone involved in the exam system to work together.
“We are reliant on the collaboration and trust of everyone involved in the exam system, and when someone commits malpractice, they let everyone down.”
She added that the “serious security breach” last Friday has been referred to the police, who have been asked to investigate it as a criminal matter.
Ms Hague added that there are various ways to ensure fair outcomes from the exam, including the option to exclude the two leaked questions from the final calculation.
Last week’s breach came after similar leaks in 2017 and 2018 when A-level maths papers were posted online ahead of the tests.
Earlier this year, Pearson said it would be trialling a scheme where microchips were placed in exam packs to track the date, time and location of the bundles.