Former Mayor Rudy Giuliani denied accusations that he hid information about dangerous airborne toxins lingering in Lower Manhattan in the aftermath of the Sept. 11, 2001 attacks — telling The Post his administration followed federal guidance.

In a new interview, Giuliani responded to questions about the city Department of Investigation recently opening a probe to determine what city officials knew about toxins in the air and when they knew it some 25 years ago.

“My administration posted everything,” the former mayor insisted, saying City Hall followed the guidance of the US Environmental Protection Agency when much of downtown reopened after terrorists hijacked planes and toppled the World Trade Center towers.

“EPA initially said everything was safe,” he said.

“I was at the end of my administration when 9/11 happened. I was told approximately 10 months after I left office that more information was known.”

Mayor Zohran Mamdani — whose administration recently agreed to release 170,000 records related to air quality concerns at Ground Zero after the terror attacks — claimed that “people got sick because the leaders they trusted lied and told them they were safe to breathe in toxic air.”

Giuliani, a frequent critic of his socialist successor, questioned whether a DOI probe under Mamdani would be fair, but said he would keep an open mind if it’s fact-finding mission.

“DOI can question me — fine,” said Giuliani, who became known as “America’s Mayor” for his leadership following the terror attacks that killed nearly 3,000 people.

“I’ll give it a chance.”

Giuliani left office at the end of December 2001 and was succeeded by Mayor Michael Bloomberg, who oversaw the reconstruction of downtown Manhattan south of Canal Street, particularly the World Trade Center complex.

One 9/11 health advocate said Big Apple officials were more concerned at the time about city’s potential liability from lawsuits than whether the air was truly clear of toxins for its residents.

“There was not a concern for the safety of the people in the neighborhood, the schools and the first responders,” said Benjamin Chevat, executive director of 9/11 Health Watch, whose group sued the city to release the long-hidden health documents.

Chevat said “I’m not going to fault people for making mistakes” during the worst terrorist attack in US history.

But he added, “It’s a little early for Mayor Giuliani to say he knew nothing.”

DOI has tapped outside lawyers to help conduct the probe what previous mayoral administrations knew about the toxic dust at Ground Zero and what, if anything, they did about it.

Lacking adequate staffing for the painstaking documents probe, the investigative agency is entering into a contract with national law firm Epstein Becker & Green to help conduct the inquiry.

“Services will include conducting an investigation to ascertain the knowledge possessed by mayoral administrations on environmental toxins produced by the September 11, 2001 terrorist attacks on the World Trade Center and to submit a report to the Council thereon,” the DOI said in a notice about the negotiated procurement.

The investigation is required by a City Council resolution passed in July 2025, with the DOI also awarded $3.8 million over a two-year period for the fact-finding probe.

Environmental activists have long claimed that city officials misled the public about toxic air risks after 9/11.

Mamdani agreed to release the secret trove of documents kept by prior administrations as part of a settlement with 9/11 Health Watch.

“For 25 years, four different mayoral administrations kept from the public, the US Congress, and the City Council documents showing what the city actually knew about the danger of the toxic chemicals in Lower Manhattan and Western Brooklyn after the World Trade Center collapse — even as city officials continued messaging to the public that the air was ‘safe and acceptable,’” Chevat said.