(CNN) New York County District Attorney Cyrus Vance's office has subpoenaed eight years of President Donald Trump's tax returns from Mazars USA, the longtime accounting firm to Trump and the Trump Organization, as part of its investigation into hush money payments, according to a person familiar with the matter.

The subpoena marks a new escalation in the large-scale effort to obtain the President's tax returns, a battle that has largely played out in courts as the Trump administration has continued to stand its ground against efforts to secure any of Trump's financial information. Trump has claimed that ongoing IRS audits have stopped him from making his tax returns public , even though audits don't prevent individuals from releasing tax returns.

Vance's office declined to comment.

The subpoena was first reported by The New York Times.

It isn't clear what deadline Mazars USA has to comply with the grand jury subpoena. The firm said it would comply with legal requests.

"Mazars USA will respect the legal process and fully comply with its legal obligations," the company said in a statement. "We believe strongly in the ethical and professional rules and regulations that govern our industry, our work and our client interactions. As a matter of firm policy and professional rules we do not comment on the work we conduct for our clients."

Any material obtained by a grand jury subpoena is covered by grand jury secrecy rules and would likely become public only if it were used as evidence at a trial.

Marc Mukasey, a lawyer for the Trump Organization, said, "We are evaluating and will respond as appropriate."

Trump and the Trump Organization reimbursed his former personal lawyer Michael Cohen for a $130,000 payment he made to adult film actress Stormy Daniels to keep her from going public with her allegation of an affair with Trump before the 2016 election. Trump has denied the affair.

Prosecutors are looking into whether the Trump Organization filed any false business records in how it accounted for the reimbursement of the payments to Cohen, a source familiar with the matter told CNN last month after the Manhattan DA's office sent subpoenas to the Trump Organization and American Media Inc.

Those subpoenas sought communications between the company and representatives for Daniels and Karen McDougal, who also alleged to have an affair with Trump more than a decade ago.

Congressional Democrats have long argued that the release of Trump's personal financial information is an important step in establishing any potential conflicts of interests involving the Trump Organization and details about Trump's financial worth.

Last month, a federal judge denied an attempt by House Democrats to fast-track its attempt to force the Treasury Department and IRS to release Trump's tax returns.

This story has been updated.