Many of the children in the pictures, who are both Jewish and non-Jewish, are infants, too young to remember the war that displaced them.

Others are teenagers who almost certainly witnessed the death of close relatives and experienced first-hand the horror of the Nazi concentration camps and forced labour.

In what may be the last opportunity to find out what happened to them, the museum is turning to social media, publishing photos from various archives on its Remember Me website.

"We're using technology in ways we were not able to in the past, especially with social networking, Facebook and Twitter, which is helping us spread the word really quickly," says Dr Lisa Yavnai, director of the museum's Holocaust Survivors and Victims Resource Center and head of the Remember Me project.

Dr Yavnai says speed is critical as many of the survivors are now in their 80s and their numbers are dwindling.

"We don't know if many of them have Facebook pages, but maybe their children and their friends do, so we hope we'll find them that way," she says.

Reuniting families

There have been countless attempts over the decades to trace Holocaust survivors and reunite them with their families.

In 1945, the BBC began a series of broadcasts on behalf of children trying to find their relatives.

One of those announcements began with the words: "Captive children - an appeal from Germany."

It continued with a dispassionate but powerful description of the trauma and suffering experienced by each child.

"I call Keevash, Moshe Keevash, last heard of in London, on behalf of his cousin Dora Keevash, a 16-year-old Polish girl. She's been through the ghetto of Lodz, a labour camp and two concentration camps, including Belsen, and lost all her family."

Anybody with information was asked to write a letter to the Red Cross.

In contrast to the cumbersome communication methods available then, today's search is already yielding results, and several survivors have been identified from their online photos.

Mr Sztulzaft's picture was seen on the museum's website within 24 hours of being posted

Michel Sztulzaft was the first to come forward.

He was little more than a toddler when he was photographed at a children's home near Paris where he and his mother had taken refuge.

Within 24 hours of his picture being posted on the museum's website, it was seen by a friend who contacted Mr Sztulzaft via Facebook.

"Seeing the photo was kind of funny," says Mr Sztulzaft. "It was a shock; I had never seen that one before."

Mr Stzulzaft's parents were originally from Poland and had been denounced during the Vel d'Hiv Round-up of 1942 - a mass arrest of Jews ordered by the Nazis and carried out by the French police.

Michel Sztulzaft with his mother in 1947 in a park in Paris. Mr Sztulzaft's mother was saved from deportation by a French policeman

His father was deported to Auschwitz, where he died, and his older brother was sent to the gas chambers.

But Mr Stzulzaft's mother, who was then pregnant with him, was saved by a French policeman who lied about her identity, claiming that she was French.

Only foreign Jews were to be arrested under the orders of that particular day.

"I think the [museum's] project, and remembering my modest story, is important because it allows us to know how, even in the darkest periods of history, there are people who do good, like the French policeman who saved my mom, who was pregnant with me, from being sent to the camps," Mr Sztulzaft says.

His mother was too traumatised to look after the young Michel, and he spent several years in orphanages operated by the Oeuvre de Secours aux Enfants, a French-Jewish humanitarian organisation that saved the lives of many Jewish children in Vichy France.

Victims of war

Mr Sztulzaft says his memories of that time were "not cheerful" and he became a "difficult child".

Dr Yavnai hopes the project will give voice to children's suffering

But he went on to marry, had two children and was happy working as a special educator.

He was also able to identify a photograph of his sister, who now lives in Israel.

"Children are often the most vulnerable victims of war and genocide but their voices are rarely heard," says Dr Yavnai.

"The Remember Me project gives the public an opportunity to give them a voice by highlighting their experiences and having time to reflect on what these children have gone through."

The story of Michel Sztulzaft and his sister Helene, along with any others that come to light, will become part of the US Holocaust Memorial Museum's permanent collection.

Anyone with information about the children pictured in the Remember Me collectioncan contact the museum's Holocaust Survivors and Victims Resource Center at RememberMe@ushmm.org.

By Jane O'Brien

BBC News, Washington