remains. The extreme heat, pressures and contamination from the collapse of the buildings has caused some of the DNA to become degraded and unusable. Samples were also degraded because some body fragments remained in the rubble for 8 to 10 months. In response to this, the medical examiner's office and other scientific groups created new techniques to process the bone fragments. The Associated Press reported that the medical examiner's office possesses "about 10,000 unidentified bone and tissue fragments that cannot be matched to the list of the dead". Bone fragments were still being found in 2006 as workers prepared the damaged Deutsche Bank Building for demolition. In order to extract the DNA, medical examiners pulverize the fragments, and compare the extracted DNA to the collection of genetic material from victims and/or their relatives, with scientists revisiting bone fragments multiple times in an attempt to identify the victims. Identification , a total of 2,753 death certificates had been filed relating to the attacks. Of these, 1,588 (58%) were forensically identified from recovered physical remains. On April 17, 2013, five possible remains were recovered after being sifted at Fresh Kills Landfill on Staten Island. The medical examiner said evidence of a possible victim of the attacks was recovered as well two days later. On June 21, 2013, the medical examiner's office matched its 1,637th victim, a 43-year-old woman, to its list of victims as a result of DNA testing of debris collected from the site. By family request, her name was not released. On July 5, 2013, the medical examiner's office identified the remains of FDNY firefighter Lt. Jeffrey P. Walz, 37, after they were retested. His remains were recovered months after the attack and was the 1,638th victim forensically identified. On August 7, 2017, the medical examiner's office matched its 1,641st victim. The victim was identified through retesting of DNA from remains recovered in 2001. In 2017 it was reported that only 1,641 victims, or just under 60%, had identified remains. On July 25, 2018, the medical examiner's office matched its 1,642nd victim. The victim, 26-year-old Scott Michael Johnson, was identified through the retesting of DNA from remains recovered in 2001. , three additional victims were successfully identified over the course of the year, bringing the total number of identified victims to 1,645. 1,108 remaining victims, representing 40% of those who perished in the World Trade Center attacks were still yet