For months, it stood as a resilient symbol of what the terrorists could not bring down. Nine stories of the World Trade Center’s north tower facade stood in thousands of tons of rubble while workers recovered bodies and cleared the site of the towers’ ruins.

When workers brought the latticework facade down in December 2001, officials said some of it would be saved. September 11, 2001, family members and others say they want to one day return the steel columns to ground zero to become part of a memorial.

But today, officials say they aren’t sure how much of that facade they have and what can be put back together. The Port Authority of New York and New Jersey, which owned the trade center and carted thousands of tons of trade center steel to an airport hangar, hired a structural engineering firm recently to examine the steel and determine what’s left of the symbolic, widely photographed facade.

“We’re trying to just find out what we have,” a senior associate at a firm run by Leslie Robertson, the structural engineer for the trade center when it was first built, Monica Svojsik, said.

Ms. Svojsik said she has been searching the steel columns in storage at a John F. Kennedy International Airport hangar for markings that would identify where it came from in the trade center, and whether it is part of the facade.

Several of those columns, including the distinctive, three-pronged trident columns that anchored the trade center towers, have been located and identified as part of the historic facade, although no steel pieces have yet been found that fit together, Ms. Svojsik said.

The Port Authority hired architects in 2001 to find historically significant pieces of steel at ground zero, and tag them for removal to the hangar, an agency spokesman, Steve Coleman, said. Almost all the other steel, including the skeletal remnants of a south tower facade that became an iconic image in the weeks after the attacks, was sent to scrap yards.

Based on the firm’s drawings and the original plans for the towers, Mr. Coleman said, the agency believes it may have saved 40% of the facade. It has hired the engineers to look at the columns “and definitively identify where they came from and how they might fit together.”

Officials have said over the years that the steel of the facade, cut into pieces because it was too large to remove from ground zero, had been saved and marked for reassembly.

“From what we were told, it was tagged in a way that it could be potentially reinstalled,” a man whose brother died at the trade center, Anthony Gardner, said. Mr. Gardner and other family members have sought to return a large part of the facade to street level when a memorial is built over the next few years.

A spokeswoman for the World Trade Center Memorial Foundation, which is developing museum exhibits for the memorial, didn’t immediately comment yesterday.

Mr. Coleman said the architecture firm had hoped that the steel columns could be reconstructed, but when it arrived at the hangar, “it was in pieces. It’s hard to determine how things all fit together.”

The Port Authority and a federal agency that investigated the towers’ collapse were the only agencies to save any trade center steel, Coleman said. “We were never told to preserve that piece, period,” he said of the facade.

The surviving columns of the destroyed towers remain the most enduring image of the towers’ destruction, Gardner said, because “they were leaning, but they never fell. The idea that it survived and stubbornly stood, despite the devastation.”