A letter ready to sent down the 250-meter pit is presented at Wangjialing Coal Mine, which straddles Xiangning County, of Linfen City, and Hejin, a county-level city within Yuncheng City, north China's Shanxi Province, on April 2, 2010. Rescuers on Friday heard the sound of knocking on pipes at the flooded mine where 153 miners have been trapped for five days. (Xinhua/Gao Xueyu)