A Dubai-based law firm run by a Quebec lawyer worked to incorporate companies in tax havens along with Panama-based Mossack Fonseca — the law firm at the centre of a leak of documents exposing the financial secrets of politicians, athletes, billionaires and drug lords around the world.

Documents reveal that Helene Mathieu Legal Consultants provided legal assistance to nearly 900 companies registered in tax havens such as the British Virgin Islands, Anguilla, Panama and the Seychelles.

Of that list, three companies have an address in Dubai and operate shell companies in the Seychelles.

All three companies have been slapped with international economic sanctions, including one for providing petroleum products to the Syrian government and another for helping deliver those products.

German newspaper Süddeutsche Zeitung obtained millions of confidential documents spanning four decades and shared them with global media partners, including CBC News and the Toronto Star, through the Washington-based International Consortium of Investigative Journalists.

Mossack Fonseca has denied any wrongdoing, saying it "does not foster or promote illegal acts."

Law firm stands by practices

None of the leaked documents from the Dubai-based firm suggest that Helene Mathieu Legal Consultants broke the law.

However, they do raise questions about what procedures law firms have in place to check for dubious activities undertaken by the companies they're incorporating in tax havens.

Hélène Mathieu, who is a member of the Quebec Bar, sent a written response to questions from CBC News and the Toronto Star, saying her firm's role was simply to compile due-diligence information on the businesses and send them to Mossack Fonseca, which then moved forward with creating the shell companies.

This 2004 photo of Hélène Mathieu appeared in a profile written by McGill University's alumni magazine. (McGill News)

"It is legal and common for companies to establish commercial entities in different jurisdictions for a variety of legitimate reasons," reads the statement from Helene Mathieu Legal Consultants.

The statement specifies that in the United Arab Emirates "offshore companies are legally and widely used to open subsidiary in free zones or to own properties," so companies can avoid being subject to Shariah law, for example, if a business partner dies.

The law firm also states that it is unable to control the operations of the shell companies once they're established.

Sanctioned for alleged 'deceptive measures'

The three companies that Helene Mathieu Legal Consultants helped incorporate and which were later sanctioned by the U.S. Treasury's Office of Foreign Assets Control (OFAC) are:

Pangates International Corporation.

Maxima Middle East Trading.

Morgan Additives Manufacturing Co.

In July 2014, OFAC accused Pangates of supplying the government of Syria with "a large amount of specialty petroleum products" which could be used for both military or civilian use, but which the department deemed had "limited civilian application in Syria."

The other two companies were later sanctioned as well, along with owners Wael Abdulkarim and Ahmad Barqawi, who were said to have "engaged in deceptive measures" to supply oil products to Syria.

The financial director of Morgan Additives, Yasser Barazi, told CBC/Radio-Canada that the company did not deliver any products to Syria before being hit by sanctions. He also said Abdulkarim left the company nearly two years ago.

Morgan Additives Manufacturing advertises its lubricating additives on its website, but the financial manager for the company told CBC News it has never completed any transactions because of economic sanctions imposed last August. (morgan.ae)

"The company has not yet provided anything. Since we were hit by the sanctions in August, we didn't have any activity," said Barazi.

"We don't have any bank account: not a local one, not a foreign one. Nothing," he said, adding that Morgan has hired a lawyer to fight the sanctions.