There is new hope for the families of hundreds of Sept. 11 victims whose remains were never identified, according to the city medical examiner, who sent letters on Thursday saying an advance in DNA technology means "new identifications will be forthcoming."

"I cannot predict how many or the time it will take," Medical Examiner Charles Hirsch said in a letter to victims' relatives. "My colleagues and I reiterate our commitment to you: We will never quit."

Hirsch said advances in DNA procedures made by Bode Technology Group, the Virginia company contracted to work on recovered Sept. 11 bone fragments, "have provided us the opportunity to renew our efforts to identify your loved ones."

Five years after 2,749 people died in the World Trade Center attack, families of about 1,150 victims still have not received word that their loved ones' remains were found. During the arduous excavation of the 110-story twin towers, which began the evening of the attacks and lasted for nine months, about 20,000 pieces of human remains were discovered.

Bode's lead forensic scientist on the project, Ed Huffine, told The Associated Press that the new process has a high success rate. The old process involved grinding down the bones and adding liquids to extract DNA from remains, he said. The new method does not dilute the sample, allowing scientists to retrieve "purer" DNA.

"What we have done over the last year is to improve the amount of DNA we recover with each sample," Huffine said in a telephone interview. "It's a much purer DNA extract. It's much easier to work with."

The city told families last year that they had exhausted all available DNA technology and were putting the project on pause until new processes were developed. The DNA in thousands of the 20,000 pieces of remains found was too damaged by heat, humidity and time to yield matches in the many tests forensic scientists have tried over the years.

Hirsch said the lab already has sent DNA profiles back to the medical examiner's office to be matched. Ellen Borakove, a spokeswoman for his office, said no new matches have been made but the technology is so encouraging that Hirsch wanted to notify the families that identifications are likely.

The news stirred mixed emotions among the families of the unidentified victims. Many of them resigned long ago to accept that their loved ones would forever be lost.

Lynn Faulkner, whose wife, Wendy, was killed, said he was torn because if her remains are among the thousands of pieces, he wants them to be identified and properly laid to rest. But he also knew how his wife felt about the significance of human remains.

"I'm sure she'd say to me, 'Look, that's not important,"' Faulkner said. "She felt very strongly that it was your spirit that mattered."