NEW YORK - The first midnight Mass at ground zero happened while workers were still clearing away the debris of the fallen twin towers and recovering bodies from the Sept. 11 terrorist attack.

The last was planned for Monday night, giving police, firefighters, ground zero workers and Sept. 11 families a final chance to pray on Christmas Eve at the site, where intensifying construction is taking up more and more open space.

"We're trying to bring closure tonight for the last six years," said the Rev. Brian Jordan, a chaplain who spent 10 months at ground zero after the attacks and has presided over every midnight Mass since then at the World Trade Center site.

"It's time to move on. It's time for us to rebuild, not just for the site, but also to rebuild our spiritual lives."

More than 150 people attended the first Mass in 2001, while thousands of workers were still removing the towers' debris and searching for bodies. "One hour before, we found the body of a fireman," Jordan said.

Since then, families of victims have come to the site every year and said a prayer for their loved ones, while several police commanders and firefighters have never missed a year.

"I see the healing that it does," said Frank Silecchia, a construction worker who has gone to every service but one. "It's like a pilgrimage."

The Port Authority of New York and New Jersey, which owns the site, has moved the service at times from one part of the site to another, depending on construction activities. Officials hope to open five office towers, a transit hub, and a Sept. 11 memorial there in the next five years.

This year, the service will be held near a trailer for Sept. 11 family members on the eastern half of the site.

Jordan said he decided to make this service the last after Port Authority officials told him that heavier construction would make a Mass in 2008 impossible. Port Authority spokesman Steve Coleman disputed that on Monday, saying that if Jordan wanted to hold future services at the site, a spot would be found.

Jordan expected about 75 people for the Mass, including the niece of a police inspector who planned to sing "Ave Maria" before family members recited prayers. Jordan was carrying a chalice dedicated to the memory of Mychal Judge, a police chaplain who was killed while performing last rites on other victims' bodies outside the trade center.

"It's just the holiest night of the year," said Jordan, "and this is sacred ground."