At least 105 people were sickened in a chemical plant gas leak in Gansu Province Monday, doctors said Tuesday.

Doctors from two hospitals in Gansu's capital Lanzhou said 105 people had sought treatment by Tuesday but none were showing serious symptoms.

Nine people have been placed under medical observation, doctors said.

The accident took place about 10 p.m. Monday as workers were refining waste oil at the Feilong Chemical Co. Ltd. in Lanzhou's Xigu District.

Pungent gas may have leaked from some of the 30 waste oil processing tanks, rescuers said.

Dozens of students from two adjacent schools immediately experienced burning in their eyes and difficulty in breathing. The school authorities called police for help.

More than 40 rescuers rushed to the site and evacuated several thousand students and residents.

Officers with the district's environment protection bureau are still trying to identify the gas.

Police officers were questioning Feng Zuolong, the private company's legal representative, and searching for workers who were at the scene when the accident happened.

(Xinhua News Agency September 8, 2009)