A 17-year-old high school student fell to his death on campus yesterday afternoon - the third case in which a student has plunged from a building in?Shanghai city in the past four days.

The student, surnamed Li, fell from the fourth floor of the school building and landed on the playground at about 1pm. The school doctor and paramedics were unable to save his life.

A preliminary investigation has ruled out murder.

Li was found carrying a knife and knife cuts were found on his arms.

He had written a letter and sent text messages to his father beforehand. Their contents were not disclosed.

A spokesperson for the student's school, Shanghai Beihong Senior High School in Hongkou District, denied that Li had suffered great academic pressure.

This was the third such incident involving students since the seven-day National Holiday break ended.

An 11-year-old boy jumped to his death from the 13th floor in his apartment building in the Pudong New Area in the early morning of Sunday, while his parents were sleeping. His body was found by a milkman at 4am.

A day earlier, a 13-year-old boy jumped from the fifth floor on campus on Yongjia Road. He was cushioned by a tree before hitting the ground. He suffered severe, but not life-threatening, injures.

The cause of his fall is still under investigation.