NEW YORK - As boxes full of victims' toothbrushes travel to laboratories in Albany and the city medical examiner's office sorts through truckloads of remains, a vast and unprecedented DNA identification effort is beginning.
Genetic testing has helped identify victims in other catastrophes, including the Oklahoma City bombing and the crashes of TWA, Egypt Air and Alaska Air jetliners.
But the victims from those incidents total fewer than 800. The number unaccounted for after hijacked planes slammed into the World Trade Center towers Sept. 11 is more than 5,000.
"Something of this magnitude, nobody has ever dealt with before," said Dr. Mitchell Holland, former laboratory chief of the Armed Forces Institute of Pathology, which analyzes DNA from major airplane crashes.
"This is not a controlled setting," Holland said. "One of the first challenges here is going to be actually locating things."
Given the condition of the wreckage, even extracting usable DNA samples might not be possible. When the World Trade Center towers collapsed, those inside were buried under the now seven-story pile of knotted steel and pulverized concrete.
"We're anticipating that we might get as much as a million samples," said Dr. Robert Shaler, director of forensic biology for the city medical examiner's office. The minimum, he said, could be 20,000 samples. "We're just going to go down this path and see what we get."
Shaler plans to test every sample. It could be weeks or months before friends and relatives of the missing get results, Shaler said. And city officials have begun to gently warn the public that there might be people who are never found or identified.
The hope is that scientists will be able to identify victims by comparing DNA extracted from remains found at the scene with samples taken from personal items and close blood relatives of the missing. Eventually scientists will create two computerized lists of genetic codes - one compiled from the donated samples, one from the remains - and look for matches.
The explosions and fire from the plane crashes, and the crushing collapse of the towers makes the task especially daunting.
"I just came back from the site," Shaler said Tuesday. "Those bodies are in lots and lots of pieces. I just don't know how they can get them all out."
Although fires no longer burn within the pile of debris, the temperature is still high. "What's happening in the building is that it's hot, like an oven, " Shaler said. "I'm not too sure DNA can withstand it. It's an unknown."
The mechanics of this experiment are still being worked out, but a preliminary plan involving hundreds of scientists and technicians from across the country is under way.
Rescue workers are placing body parts in refrigerated trucks, which are driven 30 blocks north to the medical examiner's office.
This week, two such trucks were parked outside the building, draped in American flags. Fifty-eight more are standing by for use.
Shaler's office will extract DNA samples from the remains, pack the samples in dry ice, and send them by truck or air freight to two high-volume labs, Celera Genomics Group in Rockville, Md., and Myriad Genetics in Salt Lake City, which will work on the material for reduced fees.
Myriad will perform genomic testing, the most common way to identify a person using DNA. Scientists will look at 13 regions of a person's DNA taken from a cell's nucleus and record the differing lengths - called short tandem repeats - that identify an individual.
Because a cell's genomic material deteriorates faster than other parts, Celera will do a tests on DNA found in mitochondria, which provide energy for cells. Mitochondrial DNA is maternally inherited and not unique to an individual. That means siblings and maternal relatives will have the same mitochondrial DNA.
New York City and state police labs will compile the results from both private companies using software that is being installed by the FBI.
DNA identification is a daunting task
Experts' job, matching thousands of samples, is unprecedented
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