There were a number of different such "internment camps" set up and administered differently. Knowing how the government works, I would imagine that the weight limit varied from camp to camp, and even over time. Not all Japanese, either citizens or non-citizens, were sent to these "camps", as said, each was administered differently.
Incidentally, I personal think it was the most injust action our government ever took and I'm not Japanese, I'm a "WASP".
A few years ago I visited Manzanar in California...it was almost an eerie an experience as the battlefield at Broken Knee ("Custer's Last Stand"), for at both I imagined I could hear voices from the past on the winds.
