Ten people listed by US-based Friends of Sinn Féin in Justice Department records as giving a total of $5,000 to the organisation did not make the donations, it has been established.
This came to light when three of the persons listed as making donations - many with Italian surnames and no obvious Irish connections - said in response to queries that they had not given any money to Sinn Féin.
The president of Friends of Sinn Féin, Mr Larry Downes, said that the names were listed as donors because of a "clerical error".
Mr Downes, a New York lawyer, said all the money orders in their names came from the Unity Electric Company, of Flushing, New York, whose president and CEO is Mr Peter Striano. The 10 are employed by or connected with the company.
The error occurred, Mr Downes said, when Mr Striano gave a list of guests who would be attending a fundraising dinner to clerical people from Friends of Sinn Féin, who mistook it for a list of donors.
"They misunderstood the nature of the list," he said.
The 10 men with addresses in Flushing, New York are listed as giving $5,000 to Friends of Sinn Féin, in five lists of two donors, each pair donating $1,000.
The contributions are listed as private donations, and a company name does not appear with the contributions.
One of the 10, Mr Ron Tardino, a project manager with Unity, laughed when told that he was on a Justice Department list as a Sinn Féin contributor.
"It's Unity that donates the money," he said.
"I've been to the [Sinn Féin] fundraisers before but the money's going through the company."
Another Unity Electric project manager, Mr Don Lang, also said that he didn't contribute to Sinn Féin.
"I don't have a thousand dollars to give away, but my boss does," he said.
He said that Unity Electric had given the money because it did a lot of work with a company called Structuretone.
"Unity are close friends with Structuretone, who are very Irish," Mr Lang said.
"The reason they gave this is because they work very close with Structuretone.
"I've been to all those Sinn Féin shindigs, and they charge maybe four or five thousand dollars a table," he said
"The reason my names was listed was probably because I was doing a lot of work with Structuretone then," he said.
Structuretone has made significant contributions to Friends of Sinn Féin in the past and is listed as donating $5,000 in the latest accounts.
Mr Lang said he had not contributed to Sinn Féin and suggested calling Sinn Féin to find out why his name was on the list.
Mr Tony Orsano, a Field Operations Manager with Unity Electric's New Jersey office, said that he had not made an individual donation, but said that Unity Electric had made a donation.
Mr Peter Striano, or Vincent Striano, Unity Electric's Vice President, who are also listed as contributors, did not return calls.
Sinn Féin is obliged by law to give the Justice Department a list of its donors under the Foreign Agents Registration Act.
The Act requires representatives of foreign political parties to submit accounts to the Justice Department.
Recently released returns from Friends of Sinn Féin at the Justice Department in Washington show that the organisation received almost $700,000 in the six months up to the end of April.