Police have dropped their investigation into the leak of an A-level exam paper, saying it appears no offence has been committed.

The exam board Edexcel says it is disappointed but is pursuing its own investigation and has every confidence it will get to the bottom of the matter.

It has appealed for anyone who knows anything to help.

Edexcel's inquiries have been clouded by rumours of other papers being in circulation - typically on the internet - none of which it has been able to substantiate.

Last week's leak was different in that it involved an actual photocopy of the "old syllabus" pure maths P2 module.

Shocked student told tutors

It emerged on Wednesday that a student in west London had been handed the copy of the paper - which was to be sat on Thursday morning by some 21,600 students.

The student did not pay for it, but told his private tutors he had been given to understand that papers were available for money. They contacted the authorities.

Edexcel, playing down the suggestion that many students could have seen the paper, went ahead with the exam and called in the police.

Detective Chief Inspector Richard Walton told BBC News that preliminary enquiries by officers from Camden CID had been "unable to establish any evidence of criminal offences".

He said in a statement that it was not known whether the original A-level paper had been stolen or just opened and copied.

And he said the original might have come from any of the many hundreds of sites in the UK and abroad to which the papers were distributed.

Confident

"In the absence of any further evidence that an exam paper has been stolen, Camden police are not pursuing this investigation," he said.

Edexcel's head of external relations, Beryl Jeffreys, said: "We are very disappointed that they have been unable to pursue this through to a criminal case but we have been working with them to find out how the leak happened and we are carrying on the investigation.

"We are fully confident that we will get somebody at the end of the day."

She said the exams had to rely on trust which in this case had been betrayed by "an unscrupulous person somewhere in the system".

Speaking as a parent, she was determined to get to the bottom of it, mainly for the sake of the vast majority of honest students.

"If there are people out there who are in possession of a paper, we would like to hear from them," she said.

Edexcel had had "all sorts of scaremongers" claiming that exam papers were on the internet. These had typically mentioned a number of websites, but searches had revealed nothing.