The two sisters, three and two years old, crawled into the washing machine while playing at home in Qiaoshe Township, Xinjian County of Jiangxi province last weekend.
They were found dead around noon on Saturday, police said. The girls' mother was cooking and the father was listening to music when the tragedy took place.
Their one-year-old son was also at home. Police said that the girls died of suffocation and have ruled out any foulplay, state-run Xinhua news agency reported.
Further investigation is under way. The washing machine's manufacturer, Haier, issued a statement saying that company experts have reached the scene to assist the investigation
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