In China, informal settlements are known as urban villages. Squatter settlements occurred in Hong Kong in 1946, after its wartime occupation by Japan. After 700,000 people migrated from mainland China to Hong Kong between 1949 and 1950, the squatter population was estimated at 300,000 with people sleeping wherever they could find a space. A fire at Shek Kip Mei in December 1953 resulted in over 50,000 slum-dwellers left homeless. Rooftop slums then developed, when people began to live illegally on the roofs of urban buildings.