The head teacher of an unlicensed kindergarten in southern China's Guangdong Province has been detained for questioning after the death of a four-year-old girl who was left in her car for six hours.

The suspect surnamed Lu drove her car to pick up the girl, whose identity has not been revealed, and two other children from their homes on Wednesday morning.

However, the girl was left locked in the car by Lu when they arrived at the kindergarten in Chao'an County of Guangdong's Chaozhou City, Guangzhou Daily reported yesterday.

It was not until 2pm that day that the girl was discovered in the car unconscious, according to the newspaper. A forensic report said she was suffocated to death.

Lu was detained the next day while her kindergarten was found to have been operating unlicensed for more than two years.

"Chao'an has at least 63 unlicensed kindergartens," said Ji Shaocong, the county's deputy education director. "It was a lesson to learn indicating our checks for unlicensed kindergartens was not enough."

Chao'an has launched a crackdown on unlicensed kindergartens, the newspaper said.

Only about two months ago, a kindergarten head teacher in Jiangsu Province and a school bus driver were investigated by police after a four-year-old girl suffocated to death in an overcrowded school bus taking her home.

The seven-seat minivan hired by the kindergarten in Rugao City carried about 30 children on the afternoon of February 26 including the victim Wu Yinuo, according to an earlier report by Yangtze Evening Post.

Wu suffered breathing difficulties in the overcrowded vehicle and died despite six hours of emergency treatment at a hospital in Rugao. It was Wu's second day at the kindergarten, according to her family.