NEW YORK - Human bones unearthed at the World Trade Center site in recent days are so well preserved that they will yield usable DNA, experts predicted Wednesday.

The remains - found last week after utility crews doing routine work opened up a manhole that had been paved over - are believed to belong to Sept. 11 trade center victims, 40 percent of whom have not had any remains identified.

The collection has grown to more than 130 pieces, including whole bones, shards and one-inch splinters.

"However they got there, it was certainly right at the time of the event, so they've been protected for five years and haven't been subjected to weather," said Bradley Adams, the city medical examiner's lead forensic anthropologist on site.

Bones buried with no exposure to extreme temperatures tend to be better preserved, said Ed Huffine, the head scientist on the project at Bode Technology Group, the Virginia company handling Sept. 11 bone fragments.

"I would be very optimistic about being able to obtain DNA profiles from these cases," he said.

Huffine's lab is processing fragments recently found on the roof of a skyscraper south of the site. It is much more difficult to extract DNA from those because they were subjected to rain and extreme heat and cold for years, and most aren't large enough to be tested more than once.

Families of victims with no identified remains said they felt conflicted about the recent discoveries.

"Obviously I want to know if they find something, but on the other hand it just opens it all back up again," said Lynn Castrianno, whose brother, Leonard, was killed.

The city has identified 12 underground areas that need to be explored. All are along the western edge of the site, mostly beneath a service road built in March 2002 as the excavation and recovery was still under way.