When Poles are put to work for the Germans, some peasants have access to food. The peasants succeed in smuggling food into the town and selling it to Poles on the black market. Older polish children are used as smugglers and Edek becomes a chief smuggler. As payment, Edek is given all the food he needed for his family (sisters). He hides food into the lining of his coat and sews the area up. The Germans find out about the smuggling and become vigilant. They set up patrols along the road in an attempt to catch the smugglers. Once, Edek is almost caught after he has hidden butter and eggs into a cartload of logs. The logs had been split, and the food hidden in the center then the logs glued together to concele them. A German police patrol stops the cart and Edek quickly makes off before they find anything. But he is chased and thankfully, a kind person (very likely a Polish man) lifts Edek and pitches him into a garbage cart. We learn, however, that Edek's luck soon runs out because he fails to come home one morning. After much querry, Ruth later learns that the secret police had caught up with Edek at a house where he was collecting items to smuggle. The secret police found cheese sewn in the lining of Edek's coat. They set fire to the house then take Edek, along with the house owner, away. This is the series of events that led to Edek being sent to the camp.

I could not find an instance where Edek was sent to a "Warsaw" camp - I'm wondering if you might mean the "Warthe" camp, a camp in the nearby city of Posen for victims of tuberculosis, where Edek was sent at the war's end.

Peasants had been forbidden to sell food to anyone but the Nazis in Warsaw during the war, but "with the help of the older children they smuggled it to the towns and sold it to the Poles on the black market" anyway (Chapter 7).  Edek became a skillful and daring member of one of these smuggling rings when the children were separated from their parents, but was eventually caught and sent to a forced labor camp in Germany, where he worked for two years.  He managed to escape and return to Warsaw by hiding under a truck, but this escapade, coupled with the deprivation and abuse he suffered in the work camp, took a physical toll on Edek, and he contracted tuberculosis. In the immediate aftermath of the war, Edek ended up at a transit camp in Posen, from which he was sent to Warthe because of his illness.  Always wary of being confined, Edek refused the help offered him at Warthe, and despite his poor health again struck out on his own.  He managed to get to the village of Kolina, and there, just by chance, was reunited with his siblings.