NEW YORK — The New York attorney general's office has partnered with Manhattan's district attorney to investigate Stephen K. Bannon for the alleged fundraising scam that prompted his federal pardon in the waning hours of Donald Trump's presidency, according to people familiar with the matter. The move adds prosecutorial firepower to a criminal case widely seen as an attempted end-run around the former president's bid to protect a political ally.

Investigators employed by the state attorney general were deputized to work as prosecutors with the team led by Manhattan District Attorney Cyrus R. Vance Jr. (D), whose investigation of Bannon began shortly after his pardon was announced in January, these people said. They spoke on the condition of anonymity because the investigation is ongoing.

“The AG is working hand-in-hand with the DA’s office in leading this investigation,” one person said. New York Attorney General Letitia James (D) “has been looking at Bannon for a while,” the person added.

James has built a reputation, in part, around her promises to hold Trump and his associates accountable for alleged misdeeds, and she sued his administration several times over policy decisions that affected New Yorkers. It was not immediately clear whether the scope of her interest in Bannon, who helped engineer Trump’s 2016 election victory and later served as White House strategist, goes beyond his alleged role in what federal prosecutors characterized last summer as a lucrative ploy to defraud donors of a private effort to expand the U.S.-Mexico border wall.

Vance’s investigation is focused on the same allegations charged in Bannon’s federal indictment, people familiar with the investigation said.

Bannon, along with three others, was indicted in U.S. District Court for the Southern District of New York on charges of stealing funds from their “We Build The Wall” campaign. Federal prosecutors alleged he pocketed more than $1 million after representing to supporters that all funds collected through the effort would be used for wall construction.

Bannon denied any wrongdoing, as did the others. They have not been charged with any crimes by state authorities, but the ongoing federal case does not preclude that from happening.

Bannon’s attorney Robert Costello did not respond to a request for comment. Spokespeople for Vance and for James declined to comment.

Trump’s pardon, a one-page document bearing a Justice Department seal, clears Bannon of “offenses charged” in the border-wall donation drive and “for any other offenses” that could be charged in connection to it.

Presidential pardons do not apply to state investigations.

Such collaboration between the attorney general and the district attorney is rare. The two law enforcement officials are overseeing separate inquiries into Trump and his business dealings, investigations focused on whether the values of certain assets were manipulated to gain tax benefits and favorable loan rates in violation of the state law, but it is not believed the two agencies are coordinating. While Vance is considering whether to bring criminal charges against Trump and his business associates, James is pursuing a civil investigation.

The former president has dismissed both matters as politically motivated.

As state attorney general, James has original jurisdiction over money laundering cases in New York, one person familiar with the collaboration between her office and Vance’s said, while the district attorney can prosecute any criminal offense suspected of occurring in Manhattan. It is possible Bannon could face criminal prosecution and potential civil action, although it is not clear whether such a consideration has been discussed.

Vance, a third-term elected prosecutor, will not seek reelection this year, so it is likely that any case against Bannon — or Trump — would be overseen at the trial stage by his successor.

It is also unclear whether federal prosecutors in Manhattan are assisting state investigators in their Bannon inquiry. A spokesman for the U.S. attorney’s office declined to comment.

Bannon’s three co-defendants in the federal case did not receive pardons from Trump, and the U.S. attorney’s office in New York is preparing for trial against them. Federal prosecutors are fighting the formal dismissal of Bannon’s indictment, arguing to a federal judge that Trump’s pardon does not mean the case has to be wiped from the docket, only that federal proceedings against him cannot go forward.