Hidden payments totalling £30,000 to a Tory MP's general election campaign are being investigated by the police.
The BBC has established the money for David Mackintosh's Northampton South fighting fund, in three £10,000 donations, was disguised in terms of who made them.
The Electoral Commission has passed a file on the case to the police.
Mr Mackintosh, ex-leader of Northampton council, welcomed the investigation and "will co-operate fully with police".
"I had no reason to believe that the donations were from anyone other than the named donors," he said.
In a statement to the BBC, Northamptonshire Police said: "Following an initial investigation into election fund donations made in the Northampton South constituency, the Electoral Commission has passed the information to Northamptonshire Police to continue the investigation."
A force spokesman said specialist investigators are now assessing whether there has been a criminal breach of election law.
Police are looking at the case "alongside thousands of documents obtained in the far-reaching and independent investigation into the lending of £10.25m to Northampton Town Football Club".
In April, the BBC revealed the £30,000 originated from a firm at the centre of an inquiry into the apparent disappearance of millions of pounds of taxpayers' money.
The firm, 1st Land Ltd, was passed most of a £10.25m loan made to Northampton Town Football Club by the Borough Council, intended to rebuild its stadium.
The police are already looking into "alleged financial irregularities" surrounding the loan, after the cash went missing
The Electoral Commission was then notified of the three donations, made between April and May 2014.
The BBC established the individuals concerned had links to developer Howard Grossman, who owned 1st Land Ltd, and they received the money from this firm shortly before making the payments.
Along with another firm, 1st Land received £8.75m of the council's money to facilitate the project at Sixfields, which was halted after contractors were not paid.
Mr Grossman did not comment on the new police inquiry when he was approached by the BBC.