By Gloria Pazmino

New York (CNN) — New York City is expected to release more than 170,000 pages of previously undisclosed records about air quality following the September 11, 2001, attacks, showing city officials at the time knew conditions around Ground Zero were unsafe to breathe despite repeated assurances to the public.

Mayor Zohran Mamdani is expected to announce the release Tuesday, according to city officials.

The officials confirmed the records will include contamination data gathered by local environmental agencies in the days following the attacks as well as air quality reports and communication between city officials showing there was concern about the air quality and whether the city could be legally liable as a result of the public’s exposure to the toxins.

Mamdani had previously announced the city would set aside $34 million to create a public portal to publish the documents. The disclosure is expected to give the public a better understanding of how the city responded following the collapse of the World Trade Center as officials raced to restabilize Lower Manhattan and open the area.

The documents were among 68 boxes stored in a city government office that were discovered last year and are being released ahead of Friday’s 25th anniversary of the attacks, according to city officials.

For years, survivors and first responders – including many who were sickened from exposure to toxins in the air following – have called for more transparency and demanded the release of the documents. The advocacy group 9/11 Health Watch had sued the city for release of the records. CNN has reached out to the group for comment.

Nearly 3,000 people were killed on 9/11, but thousands more – including first-responders who spent months working at the site – have since died from 9/11-related cancers and other illnesses.

Mamdani is expected to appear alongside 9/11 families and Jon Stewart, a longtime advocate for increased transparency and resources for first-responders and survivors.

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