Another two batches of school uniforms have been found with cancer-causing dyes, according to Shanghai's quality watchdog.

The Shanghai Municipal Quality and Technical Supervision Bureau said on Monday that it has received 106 batches of samples of school uniforms produced by Shanghai Ouxia Clothing Company, which were found to have used banned dyes in previous checks.

Among these 106 batches, two were found to contain the carcinogenic substance.

In a previous test, the city's quality watchdog examined 22 batches of uniforms, including tops and trousers, and six batches failed the quality test. Some of six batches contained toxic substances.

Items produced by Shanghai Ouxia Clothing contained aromatic amine dye, which can cause cancer, it said.

Schools that purchased clothes from the company are required to stop using the uniforms, and submit them for testing.

So far, the company has halted production for investigation. All the remaining clothes and materials have been sealed.

Authorities said it will increase the tests on school uniforms and is considering adopting a centralized purchase model to better supervise the quality of school uniforms.