HARBIN, China -- The death toll from a roof collapse in a school gymnasium Sunday in Qiqihar City, northeast China's Heilongjiang Province, has risen to 10, rescuers said Monday. As of 5:30 a.m. Monday, rescuers had brought out 14 people from the debris. Among the casualties, four were confirmed dead on the spot, and six others died after full medical treatment. The remaining four people have been checked without life-threatening injuries. There were 19 people in the gymnasium covering about 1,200 square meters at the No. 34 Middle School of Qiqihar in Longsha District when the accident occurred. Four people escaped on their own and 15 were trapped, the municipal search and rescue headquarters said. A preliminary investigation found that construction workers illegally placed perlite on the roof of the gymnasium during the construction of a teaching building adjacent to the gymnasium. Under the influence of rainfall, the perlite soaked up water and gained weight, resulting in the roof collapse. An in-depth investigation is ongoing. Those in charge of the construction company have been taken into police custody.