A preliminary investigation shows human error may have caused a deadly accident involving a high-speed passenger train and another train. At least 70 people were killed, and more than 400 injured in Monday's accident.

Photo taken on April 28, 2008, shows the site of the trains  colliding accident, in east China's Shandong Province. Passenger  train T195 en route from Beijing to Qingdao city in eastern China  derailed and hit train 5034 early on Monday, causing "heavy  casualties", witnesses and a government spokesman confirmed. (Xinhua Photo)

The Qingdao-Jinan Railway reopened to traffic Tuesday morning after an interruption of over 20 hours.

This is China's worst train accident in over a decade.

The tragedy happened before daybreak on Monday in Hejiacun village about 500 meters east of Wangcun Railway Station in Zhoucun District in the suburbs of Zibo city.

A high-speed train from Beijing to Qingdao derailed. And a train on its way from Shandong to Jiangsu province then slammed into it. The second train also veered off the tracks. A total of at least 12 carriages from both trains derailed.