UPDATE 1-PM May's spokeswoman denies to comment on investigation in Brexit campaign funding

British Prime Minister Theresa May's spokeswoman said on Thursday she was unable to comment on the ongoing criminal investigation into the funding of the pro-Brexit campaign.

Earlier, Britain's serious crime agency began an investigation into Brexit-backer Arron Banks and one of the main groups which campaigned to leave the European Union. The agency is questioning the true source of millions of pounds in loans.

"I can't comment on an ongoing investigation," the spokeswoman said.

When asked about allegations of possible Russian influence on the vote, she said: "There is no evidence to suggest that is the case."