Trump Organization chief financial officer Allen Weisselberg surrendered to the Manhattan district attorney's office Thursday morning ahead of expected criminal charges against him and the company in connection with alleged tax crimes, his attorney told CNN.

Weisselberg is set to be arraigned later Thursday at a lower Manhattan courthouse. Weisselberg's attorneys, Mary Mulligan and Bryan Skarlatos, said he plans to plead not guilty and “will fight these charges in court.”

A Manhattan grand jury filed the indictments Wednesday, and they are set to be unsealed Thursday around 2 p.m. ET, according to two sources familiar with the matter. The precise type or number of charges they are expected to face was not immediately clear.

Though former President Donald Trump faced multiple federal and state prosecutorial inquiries during his administration, the district attorney's indictment would be the first to charge his namesake company, the Trump Organization, for conduct that occurred when he led it.

Trump himself is not expected to be charged, his attorney has said.

The indictment of the Trump Organization is the product of more than two years of investigation by the district attorney, Cyrus Vance Jr., a probe that began with questions about accounting practices tied to hush-money payments made by former Trump lawyer Michael Cohen and eventually led to a Supreme Court fight over a subpoena for Trump's tax documents.

It is rare, according to lawyers who specialize in tax evasion cases, for prosecutors to bring charges solely related to fringe benefits provided by a company, and in recent weeks, lawyers for the Trump Organization met with prosecutors in Vance's office, hoping to persuade them not to bring the case.

The Trump Organization released a statement Thursday saying that Weisselberg is being used by Manhattan prosecutors “as a pawn.”

“The District Attorney is bringing a criminal prosecution involving employee benefits that neither the IRS nor any other District Attorney would ever think of bringing. This is not justice; this is politics,” said the statement, attributed to a spokesperson from the Trump Organization.

Over the course of the probe, prosecutors have examined a wide array of possible violations, including whether the real-estate company misled lenders and insurers or committed tax fraud, even adding a special prosecutor, Mark Pomerantz, to aid in the expansive inquiry. But in recent months, the focus has narrowed to taxes on benefits.

In particular, it came to centre on Trump's longtime lieutenant Weisselberg, a top company executive who has worked for him since 1973.

Beginning late last year, prosecutors gathered evidence on Weisselberg with the cooperation of his former daughter-in-law, Jennifer Weisselberg. In the months since she began speaking to authorities, she has turned over boxes of financial records and has met with investigators multiple times, her lawyer told CNN.

Documents from Jennifer Weisselberg's divorce from Allen Weisselberg's son Barry show thousands of dollars in payments for cars, rent, tuition, medical bills and more going from Allen Weisselberg to his son's family.

An indictment of Weisselberg would intensify the pressure for him to cooperate with prosecutors in their wide-ranging investigation of Trump, the company and its executives, an outcome prosecutors have been seeking for months but which his lawyers have told authorities he has rejected.