The Manhattan District Attorney’s Office headed by Cy Vance has sent a grand jury subpoena to President Donald Trump’s accounting firm to get his tax returns and corporate tax returns for the past 8 years, a person with direct knowledge of the matter tells NBC News.

The subpoena, first reported by the New York Times, stems from Vance's criminal investigation into the Trump Organization about payments made to two women who have alleged affairs with the president.

Legal experts with such requests says that the subpoena will likely focus not just on the tax returns but will likely also ask for the underlying documents used to generate the tax returns such as bank statements, expense statements, and other financial documents.

The subpoena was served on Mazars USA, which prepares the president’s tax returns.

A representative for Mazars USA said that as "a matter of firm policy and professional rules we do not comment on the work we conduct for our clients," but the company "will respect the legal process and fully comply with its legal obligations."

When asked about the subpoena's legality, Trump told reporters on Monday that "I don’t know anything about it." The president’s attorney, Marc Mukasey, told NBC News, "we are evaluating the situation and will respond as appropriate."

A spokesperson for the Manhattan District Attorney’s Office declined to comment.

In addition to Trump's company, the D.A.'s office also subpoenaed the publisher of the National Enquirer, which was involved in negotiations with adult film star Stormy Daniels and paid $150,000 to silence another woman who'd claimed she had an affair with Trump, Playboy model Karen McDougal, the Times has reported.

The president has strongly denied the affairs.

The president’s personal attorney, Michael Cohen, last August admitted to making the illegal payment to Daniels in order to keep her quiet in the days ahead of the 2016 election.

Cohen is currently serving a three-year prison sentence for a slew of crimes, including breaking campaign finance laws by hiding payments related to the alleged affairs.

Prior to his Congressional testimony earlier this year Cohen released copies of two checks with the president’s signature that he says were used to pay him back for his $130,000 payment to Daniels.

NBC News has previously reported that Cohen has proffered information to prosecutors from the D.A.’s office.