Students from 21 primary and secondary schools in Shanghai have been told to stop wearing their school uniforms because they contain toxic substances.

According to the Shanghai Quality and Technical Supervision Bureau, six out of 22 batches of school uniforms failed quality tests, and some of them were found to have toxic substances.

School uniforms produced by the Shanghai Ouxia Clothing Co Ltd were found with aromatic amine dyes, which can cause cancer, it said.

Local Chinese media reported that some 21 schools have ordered school uniforms from the factory.

The bureau is carrying out an investigation into the factory.

On Feb 17, the Shanghai Municipal Education Commission required the 21 primary and secondary schools to send the uniforms for tests.