A recent investigation by the Shenzhen Consumer Council has found that several brands of mobile phone covers, including from big names Apple and Xiaomi, contain toxic and harmful substances that have exceeded the limit and could harm people's health.

The council investigated 30 popular mobile phone covers from 28 brands, including Apple, Samsung, Huawei and Xiaomi.

Five brands of covers were found to have toxic and harmful substances that exceeded the standard limit. Among them are Apple and Xiaomi covers sold on their respective official websites.

The level of lead in one cover featuring shimmering powder from the Chinese band Yuening is even 1,550 times greater than the limit.

The substances are mainly lead, polycyclic aromatic hydrocarbon and plasticizer, which could damage organs and even lead to cancer, an official from the council said.

According to the council, most consumers, 67 percent, choose to buy mobile phone covers online. Nearly 90 percent of consumers buy mobile phone covers priced below 50 yuan ($8).

Users of Apple, Huawei and Samsung mobile phones like buying covers the most.

Official statistics show that the number of Chinese mobile phone users reached 1.42 billion last year. About 75 percent, or 1 billion, use covers.

Nearly 70 percent of mobile phone covers across the country are produced in Shenzhen, with the annual market value amounting to 20 billion yuan.