Inspectors visited 3,600 businesses in Dongguan, a major industrial center in the Pearl River delta, China Daily reported. Most of the children were found in small factories.

"In the factories we inspected, we did not come across any large-scale use of child labor," Li Xiaomei, deputy mayor of Dongguan, said at a press conference.

She said companies that violated the law face fines of $7,200.

The children were between the ages of 9 and 16 and had been brought illegally from Sichuan in western China, one of the country's poorest provinces.

Dongguan is in Guangdong Province on China's southeast coast. The province, the most populous in China, has become a major industrial center.