An explosion at a chemical plant Monday in the central city of Guiyang left five people injured and forced some 20,000 others to leave their homes, China's official Xinhua news agency said.

The incident occurred around 10:20 a.m. at a factory of the Bestchem company whose principal product is pyrethoid, a substance used in pesticides.

Following the explosion, all inhabitants within a radius of 1.5 kilometers (1 mile) were ordered to evacuate, including students on the campus of Baiyun University.

The five injured were factory employees.

According to preliminary investigations, the explosion was caused by a leak of toluene and methanol, though at first the devices that monitor pollution rates did not detect an increase of harmful gases in the atmosphere.

Authorities said the fire that set off the explosion has been extinguished, and that the local government continues to monitor air and water quality in the affected area.

Industrial accidents are relatively frequent in China due to the lack of safety measures. Reports over the past 10 years speak of such accidents occurring every other day. EFE