September 11th 25 Years Later: A Call for Further Investigation

Dear Editor,

Due to the extraordinary efforts of the New York City Office of the Chief Medical Examiner (OCME), remains associated with the September 11, 2001, terrorist attacks continue to be identified. Nevertheless, despite the longest and most expensive forensic investigation in history, 40% of the 2,753 victims at the World Trade Center remain unidentified. In her 2009 PhD dissertation, Amy Mundorff singled out commingling caused by the building collapses as one of the factors that had impeded identification:

The explosive force that blew over fire trucks and peeled stone facades from buildings also disintegrated human bodies, turning bones into flying shrapnel that became embedded in soft tissue from other individuals. The tidal wave of debris that carried human remains blocks away, depositing them in some cases on top of buildings, also fused soft tissue to bone fragments from multiple individuals so completely that the remains appeared to be from the same individual [1].

The disintegration resulted in a level of fragmentation rarely seen, which created unprecedented forensic complexity [2]. In nearly 5,000 cases, the remains were smaller than an inch, and they were “often difficult to distinguish from inorganic material” [1, 3]. In one extreme case, 176 fragments were linked to a single individual.
    Two papers by Adams et al. in Forensic Science International clarified that 21,905 remains had been recovered, of which 14,750 had been matched to 1,647 of the 2,753 victims, leaving 1,106 unidentified by September 11, 2021 [4-5]. Excluding the terrorists and victims aboard United Airlines (UA) 175 and American Airlines (AA) 11, the average and median body completeness values were only 41% and 25%, respectively, for the 1,322 people inside the Twin Towers whose remains had been identified. Based on their last known location, the percentages of unidentified victims at and above the impact zones were 42.8% in the North Tower and 40.7% in the South Tower. For victims below the impact zones, the percentages were 37.2% and 33.3%, respectively. However, the correlation was not statistically significant. There were, by contrast, significant differences in the identification rates between UA175 (46.7%) and AA11 (77.0%). The leading hypothesis is that the difference was due to UA175 traveling about 160 km/h faster than AA11 at the time of impact.
    Subsequent to the destruction of the buildings, hazardous conditions existed for months that contributed to the deterioration of the human remains. Within days of the event, thermal hot spots of up to 747°C were recorded by the U.S. Geological Survey using NASA’s Airborne Infrared Imaging Spectrometer [6]. Despite the use of Pyrocool FEF, a chemical fire suppressant, and massive quantities of water, the highly unusual fires were first officially extinguished on December 20, though isolated pockets of extremely high temperatures may have persisted into February 2002 [7].
    In gravity-driven structural failures, we would expect to observe blunt force trauma, mechanical asphyxia, lacerations, fractures, and crush injuries, as well as the resulting crush syndrome [8]. The documented body disintegration beyond identification, commingling, and extreme fragmentation of the remains at the World Trade Center stand in contrast to these expected outcomes. A case in point is the 13 employees of General Telecom (GT) who were trapped on the 83^rd floor of the North Tower. They communicated with the outside world until collapse ensued. Despite more than two decades of DNA testing, none of their remains has been identified. Similarly, all victims whose last known locations were on the 80^th and 79^th floors of the North Tower, and the 44^th floor of the South Tower, remain unidentified [4].
    The George W. Bush administration tasked the National Institute of Standards and Technology (NIST) with providing a full technical explanation for how the buildings collapsed. The structural behavior would conceivably provide a plausible mechanism for the spectrum of injuries. Despite producing some 10,000 pages, NIST engineers “did not analyze the collapse of the towers,” and admitted they were “unable to provide a full explanation of the total collapse” [9-10]. Instead, they only accounted for the sequence of events leading to collapse initiation, after which they asserted that “collapse became inevitable” [9]. For this reason, NIST did not study the post-collapse conditions, which could have elucidated the extent to which they contributed to the low identification rate.
    Private research groups have produced one-dimensional collapse models, but they have significant limitations, which include contradicting video footage of the collapse of both buildings [11]. Moreover, none of them contain the necessary resolution to account for the structural behavior on a floor-by-floor basis that would enable predictions regarding fragmentation, commingling, and victim identification rates.
    The scientific community is urged to investigate further and provide answers to these issues. While many families suffered immensely by having to bury empty coffins or only fragments of their relatives, the scientific community could assist by explaining why this occurred. Ultimately, it is highly unlikely that all the remains will ever be identified. Relying on the Good-Toulmin estimator, Adams et al. calculated that there would only be 76 new identifications over time; hence, they concluded that over a thousand victims “may never” have their remains identified [5].

References

[1]. Mundorff, Amy. “Human Identification Following the World Trade Center Disaster: Assessing Management Practices for Highly Fragmented and Commingled Human Remains.” 2009. Simon Fraser University, PhD dissertation. Summit Research Repository. Link: https://summit.sfu.ca/item/9782 [accessed April 2026].
[2]. Mundorff, A., R. Shaler, E. Bieschke, and E. Mar-Cash. “Marrying Anthropology and DNA: Essential for Solving Complex Commingling Problems in Cases of Extreme Fragmentation.” In Recovery, Analysis and Identification of Commingled Human Remains, edited by B. Adams and J. Byrd, pp. 285-300. Humana Press, Totowa (2008).
[3]. Biesecker, Leslie G et al. “Epidemiology. DNA identifications after the 9/11 World Trade Center attack.” Science (New York, N.Y.) vol. 310,5751 (2005): 1122-3. doi:10.1126/science.1116608.
[4]. Adams, Bradley et al. “Victim identification and body completeness based on last known location at the World Trade Center.” Forensic science international vol. 340 (2022): 111440. doi:10.1016/j.forsciint.2022.111440.
[5]. Adams, Bradley et al. “Victim identification from the September 11, 2001 attack on the World Trade Center: Past trends and future projections.” Forensic science international vol. 340 (2022): 111463. doi:10.1016/j.forsciint.2022.111463.
[6]. U.S. Geological Survey. Images of the World Trade Center Site Show Thermal Hot Spots on September 16 and 23, 2001. Open-File Report 01-0429. U.S. Department of the Interior (2001). Link: https://pubs.usgs.gov/of/2001/ofr-01-0429/thermal.r09.html [accessed April 2026].
[7]. “Recovery worker reflects on months spent at Ground Zero.” May 29, 2002. Knight Ridder Newspapers (Jennifer Lin).
[8]. Ciottone, G. R., et al. (Eds.). (2016). Ciottone’s Disaster Medicine (2^nd ed.). Elsevier. https://hsrc.himmelfarb.gwu.edu/books/67/ [accessed May 2026].
[9]. Sunder et al. Federal Building and Fire Safety Investigation of the World Trade Center Disaster: Final Report of the National Construction Safety Team on the Collapses of the World Trade Center Towers (NIST NCSTAR 1), National Construction Safety Team Act Reports (NIST NCSTAR), National Institute of Standards and Technology. https://doi.org/10.6028/NIST.ncstar.1.
[10]. Fletcher, C. S. (2007, September 27). Letter in response to April 12, 2007 request for correction regarding the Federal Building and Fire Safety Investigation of the World Trade Center Disaster. National Institute of Standards and Technology. Link: https://archive.org/details/nist_20260508 [accessed May 2026].
[11]. Schneider, A. (2017). The Late Jolt – Re-Examining the World Trade Center Catastrophe. arXiv. https://doi.org/10.48550/arxiv.1712.06207 [accessed