NEW YORK >> Albert Ogletree, a food handler with Forte Food Service, was working in the cafeteria at Cantor Fitzgerald in the north tower of the World Trade Center when a hijacked jetliner careered into the skyscraper. He is one of the 2,983 people killed in the terrorist attacks of Sept. 11, 2001, and Feb. 26, 1993, when the trade center was bombed.

He is also one of only 10 victims whose portraits are not in the vast gallery at the National September 11 Memorial Museum, on the trade center site in Lower Manhattan. Museum officials have tried for years, without luck, to find someone who can furnish a picture of Ogletree — on vacation, perhaps; under a mortar board at graduation; beaming with happiness at his wedding; or hunched over a sketch pad drawing cars, something he loved to do.

Faces have defined the events of Sept. 11 since the earliest hours. On lampposts, bulletin boards and hospital walls, “Missing” posters beseeched passers-by to recall whether they had seen this face or that. Faces filled the pages of The New York Times and other publications and websites. Portraits were carried, facing the public, by survivors at memorial services and protest gatherings.

The museum’s goal is simple and increasingly challenging: to gather every face and weave it into the overwhelming tapestry of grief, loss, life and joy on display in the memorial gallery.

“Our objective from the get-go was to make sure that anyone declared a victim is depicted on that wall,” said Jan Seidler Ramirez, the museum’s chief curator.

Those victims include everyone killed on Sept. 11 in New York, at the Pentagon and in Shanksville, Pennsylvania, as well as the six people killed in the 1993 bombing.

“To make that connection to the names outside, that’s really at the heart of our mission,” Ramirez said. “We’re not about abstract statistics. We’re about honoring each and every person who was killed that day, creating an opportunity for friends and family to see the faces they loved.”

Three families have told museum officials they do not want their relatives’ portraits shown publicly. That leaves seven to find.

The gallery has room for 3,000 5-by-7-inch portraits, arrayed in 250 columns and 12 rows. The 10 victims whose portraits are missing can be found in their alphabetical spots. Instead of a face, each is represented by a single leaf, green tinged with red, of a swamp white oak, the kind planted on the plaza, where the victims’ names are inscribed in panels around twin memorial pools.

The missing pictures the museum seeks are of Gregorio Manuel Chavez, 48; Kerene Gordon, 43; Michael William Lomax, 37; Wilfredo Mercado, 37; Ogletree, 49; Antonio Dorsey Pratt, 43; and Ching Ping Tung, 44. (Visitors to the gallery can pick out the other three by finding the oak leaves and accompanying names. Given their families’ wish for privacy, The Times is not identifying them.)

Four of the seven — Chavez, Gordon, Ogletree and Pratt — worked in food service, suggesting that they came from lower-income families whose public footprint may not be too large. And whether those killed were poor or rich, their survivors might well have moved away from New York. Addresses have grown out of date. Telephones have been disconnected. Trails have gone cold.

It has been 15 years, after all.

Gathering nearly 3,000 portraits, an extraordinary enterprise in itself, began long before the museum opened.

The first cache, Ramirez said, came from the Justice Department, which had assembled photographs to introduce as evidence at the trial of Zacarias Moussaoui, the so-called 20th hijacker in the Sept. 11 plot. Those proceedings ended in 2006.

Then came head shots from the New York Fire and Police Departments, the Port Authority Police Department and companies or institutions with a large presence at the trade center, like Cantor Fitzgerald, Aon, Marsh & McLennan and the Windows on the World restaurant. One-third of all those killed at the trade center on Sept. 11 were either firefighters or Cantor employees.

The biggest step forward came with the collaboration of a group called Voices of September 11. Its 9/11 Living Memorial is composed of images and remembrances from family members. The group asked contributors if the content of their tributes could be transferred to the museum. Nearly 500 said yes, Ramirez said.

By the time the museum opened in 2014, 21 portraits were missing. More than 100 have either been added or replaced with better pictures or higher-quality versions of existing portraits.

“We’re constantly trying to figure out how to find somebody who keeps the memory candle lit who can help us,” Ramirez said.

This month, The Times’ research desk joined the search.

>> Chavez: Born in the Dominican Republic, he worked at Windows on the World. Calls to his widow were not returned, Ramirez said, and attempts to reach a niece and a nephew were fruitless. The Times found a woman living in Manhattan who may be his sister and forwarded her contact information to the museum; it did the same with information for a man who may be Chavez’s son.

>> Gordon: She came to New York from Kingston, Jamaica, and worked for Forte as a food handler. Ramirez said the museum had been in touch with her son and her sister in 2012 and 2014, but no picture had materialized. The Times found the name of a woman in Queens who may be a relative and sent it to the museum.

>> Lomax: A native of Manchester, England, Lomax was an executive at Aon. He lived in Brooklyn. Three efforts to reach his widow were unavailing, Ramirez said, and the September 11 UK Families Support Group did not have his picture. The Times printed a head shot of Lomax in 2002 and provided the museum with leads to his widow and to his father.

>> Mercado: He was a purchasing agent for Windows on the World and was killed in the 1993 bombing. Born in Lima, Peru, Mercado lived in the East New York section of Brooklyn. Ramirez said the museum had “tried extensively” to reach his widow. The Times found what appears to be a picture of Mercado on the Facebook page of one of his daughters and forwarded what may be her telephone number to the museum.

>> Ogletree: He came from Michigan. A “distant cousin” has told the museum he might be able to locate a photograph and send a copy to the museum, Ramirez said.

>> Pratt: A native New Yorker, Pratt worked as a food handler for Forte. “The next of kin had a disconnected phone,” Ramirez said. “There was no email address and nothing but returned letters from the address of record.” She said the museum was now working on leads with the Windows of Hope Family Relief Fund, which serves survivors of those who worked in the food, beverage and hospitality industries.

>> Tung: A resident of Queens and native of Hong Kong, Tung was employed at the First Commercial Bank. Letters to his widow were returned as undeliverable in 2012, 2013 and 2014, Ramirez said, and there was no answer at a home telephone number. The Times learned that Tung might have gone by an Anglicized first name and provided the museum with the phone number of someone in Queens whom he may have known.

“There is no trail we will not pursue,” Ramirez said.

Now there are a few more.

© 2016 The New York Times Company