Two more students at a primary school in Yueqing, Zhejiang province, suffered nosebleeds, bringing the total number of children affected by what are suspected to be exhaust emissions from surrounding factories to 21, according to the Oriental Morning Post.

Students at Beibaixiang township No 9 Primary School moved to the old campus to resume classes on Monday after 19 of them suffered nosebleeds and headaches the day before. Now two more students have suffered the same problem, according to the city's department of health.

Preliminary tests by the local environmental department showed an acidic mist that exceeded the discharge standard in the exhaust emissions from factories nearby.

The concentration of methanol in the newly built school building might also be the culprit, according to the environmental authority.

The pollution source of the incident is under investigation.