Palestinian workers are seen at the only factory to manufacture sewage pipes at Karni industrial zone in northern Gaza Strip on March 12, 2013. (Xinhua/Wissam Nassar)

A Palestinian worker is seen at the only factory to manufacture sewage pipes at Karni industrial zone in northern Gaza Strip on March 12, 2013. (Xinhua/Wissam Nassar)

Palestinian workers are seen at the only factory to manufacture sewage pipes at Karni industrial zone in northern Gaza Strip on March 12, 2013. (Xinhua/Wissam Nassar

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Palestinian workers are seen at the only factory to manufacture sewage pipes at Karni industrial zone in northern Gaza Strip on March 12, 2013. (Xinhua/Wissam Nassar)