More: Key findings from the documents, which were reviewed by The New York Times before Tuesday's announcement, include:

Asbestos and other contaminants were found at levels that exceeded acceptable levels in dust and air in part of lower Manhattan, based on measurements taken by city agencies, the Environmental Protection Agency and privately contracted laboratories.

A draft document of data compiled by the city Department of Environmental Protection listed locations throughout lower Manhattan where asbestos levels in dust samples exceeded hazardous limits in the days after September 11.

A November 2011 audit, prepared by a private company and submitted to the EPA, showed the amount of the carcinogen benzene was still spiking in the air around the towers' footprints.

That audit also showed that the concentration of asbestos in the air at the Fresh Kills landfill on Staten Island has increased after the attacks.

A woman who lived in lower Manhattan wrote a letter to the DEP in Feburary that detailed alleged missteps by officials in removing contaminants from in and around her building, where workers dug up grass and dirt from a small roundabout in the neighborhood several weeks after 9/11.

The documents were discovered last year after being hidden from the public in 68 boxes stashed in a government office, city officials told the NYT.