An A-level maths paper was allegedly leaked on the internet the night before thousands of students sat the exam.

The exams watchdog Ofqual said it was working with Pearson, the company that owns the Edexcel exam board, “to establish the facts” after the C4 maths paper apparently appeared for sale online on Thursday night.

Students reported seeing the paper for sale at £200, with sellers said to be offering the first question for free to prove they had it.

@Edexcel paper got leaked last night and came up in the exam. please do something about this; it is completely unfair to those of us that actually worked hard for our maths grades. pic.twitter.com/G1axmtCkc6 — 🍒 (@fxdx_fydy) June 22, 2018

Ofqual said in a statement on Friday: “We are aware of the allegations of malpractice or wrongdoing in relation to Edexcel’s C4 maths paper taken today. We are working with Pearson to establish the facts.

“We recognise the concerns of students, who should continue to prepare for their forthcoming exams as normal. If anyone has information relevant to these allegations we would urge them to contact Pearson or us in confidence.”

It is not the first time Pearson has been rocked by leaked exam papers. Last year it was forced to amend two maths papers at the last minute after reports some students had gained access to them in advance.

In a statement made through the Edexcel Twitter account, Pearson said it was aware of claims of “a limited breach of security”.

“As is usual practice in these circumstances, we have opened an investigation into whether there has been any exam malpractice. We are also contacting the police on this issue.

“We’d like to reassure all students that the planned exams next week will continue as scheduled and that we have established processes in place to ensure no students will be advantaged or disadvantaged in any way.”

Students who sat the exam discussed on social media their fears that they may be forced to resit, and their anger at the exam board over the leak.

“I am actually so angry. Some of us gave our all to these exams so we could be proud of the grades we get at the end,” one student tweeted. Another said: “This is disgusting. It’s totally unfair on the people doing everything they can to get a grade.”