A spokesman for the port city said disciplinary supervision authorities are were looking into whether officials allowed the substandard uniforms to enter school campuses, China's state-run news agency Xinhua reported Monday.
As of Sunday, two of 106 lots of school uniforms produced by the Ouxia Garment Co. were confirmed to contain cancer-causing azo dye, the city spokesman said.
Student uniforms for 41 schools in Shanghai were either produced by the firm or labeled with its "Ouxia" brand.
Education officials ordered 26,400 elementary and secondary students to stop wearing Ouxia-brand school uniforms Feb. 18 after a quality inspection effort found azo in some of the uniforms.
Xinhua said education and quality inspection departments have bolstered school uniforms inspections and have asked all schools to submit samples of their uniforms for testing before distributing them to students.