Human bones unearthed at the World Trade Center site in recent days are so well preserved that experts predicts they will yield usable DNA — leaving some suvivors of those killed on Sept. 11 with conflicted feelings five years after the attacks.

"We're all wondering again if we're going to get that call," said Lynn Castrianno, whose brother, Leonard, was killed. "Obviously I want to know if they find something, but on the other hand it just opens it all back up again."

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

The collection has grown to nearly 200 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 Wednesday.

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.

Thousands of bone pieces recovered during the main excavation still have not yielded matches, leaving more than 40 percent of the attack's 2,749 victims without any trace of remains.