Polish archaeologist Zbigniew Sawicki gestured at three tiny bones, which were browned by years in the clay soil of northern Poland.
"This must have been a tiny child," he told AFP.
Emerging from a pit at the construction site of a luxury hotel in this tourist town, the remains of hundreds of German civilians have offered a stark reminder of Europe's World War II history, six decades after the end of the brutal conflict.
Workers stumbled on the mass grave on October 28, and since then experts have exhumed 1,800 remains.
Malbork was once part of German-ruled East Prussia and was known as Marienburg, but became Polish following post-war border changes.
The town is best-known as the home of the mediaeval castle of the Order of Teutonic Knights, which is one of Poland's most popular tourist attractions
and lies around 300 metres (yards) from the pit.
Investigators believe the grave was dug in 1945, as the Soviet Red Army arrived from the east, rolling back Nazi German forces on the road to victory in Berlin in May 1945.
"They were of all ages. All of them were buried naked. Around 30 had bullet holes in their skulls," Sawicki said. "Otherwise, there's nothing. No items, nothing metal, no glasses, rings or even false teeth. Nothing that could help us identify the victims," he explained.
His team believes that many of them perished in aerial bombardments and fighting, from starvation or hypothermia - and that some may have been executed.
The bullet-holed skulls were found at the top of the pit. Sawicki said those victims may have been shot after having been forced to gather dead bodies around the town and throw them into the mass grave.
"If we haven't found any clothing, that's because it was likely burned out of fear of a typhus epidemic," he noted.
The mass grave's existence was unknown until construction workers stumbled on it, said Piotr Szwedowski, secretary of Malbork town hall, explaining that there was no trace in the municipal archives.
"It must date back to the period when most of the Germans had already left the town, which was in Soviet hands," he suggested.
The first Polish records from Malbork begin in May 1945, when Polish settlers arrived in the town, most of them from Poland's former territory in the east which had been declared part of the Soviet Union.
Some 30,000 people lived in German-era Malbork. In early 1945, the town was the site of savage battles between Soviet and Nazi forces.
As the Red Army had neared, Malbork's residents were ordered to evacuate deeper into German-controlled territory.
According to Rainer Zacharias - a German historian who hailed from the town and published a book about the period in 1967 - the last refugee train left on January 24, 1945.
German troops held out in the castle until March 9.
Zacharias wrote that some 3,000 residents had stayed behind despite the evacuation order, and that the fate of 1,840 of them was unknown.
The fact that a similar number have been exhumed has fuelled speculation that the mystery has at last been solved.
But local prosecutor Waldemar Zduniak, whose office has opened an investigation, was cautious.
"We're not historians. We're prosecutors. We need evidence. We're looking for witnesses, particularly in Germany, who could shed light on what happened," he said.
The discovery has raised hopes for former residents that they will learn the fate of long-lost loved ones.
Franz-Rudi Neumann, 83, who now lives in Luebeck in northern Germany, said he was sure his grandmother was among the dead.
"At the time she must have been about 80. She'd broken her leg and couldn't walk," he said.
"I hope she will finally get a decent burial, and that it will be in Marienburg, her home town," he said.