Two companies based in Shenzhen in South China's Guangdong Province have been confirmed to have hired nine child laborers, local authorities said Monday.

The subdistrict office of Fuyong Street in Bao'an district announced that Shenzhen Click Technology Co Ltd and Shenzhen Datlink Electronics Co Ltd were proven to have employed nine child laborers under the age of 16.

Authorities are verifying the age and identities of another 20 suspected child laborers.

Local media reported at the end of 2013 that Shenzhen Click Technology Co Ltd was suspected of hiring dozens of child laborers from Liangshan Yi Autonomous Prefecture in Southwest China's Sichuan Province.

According to the media report, the children, mostly girls, had to work 12 hours a day and earned a monthly salary of only 2,000 yuan ($330).

The children have already been sent back to their homes.

The human resource bureau of Bao'an district ordered the two companies to correct their practices, and fined them 10,000 yuan and 35,000 yuan respectively.