The poor living and school conditions of the children of migrant workers hit the spotlight again on Thursday after it was announced that a 6-year-old girl in Central China had contracted a sexually transmitted disease (STD).

Doctors are still puzzled how the girl, who they referred to by the alias Qianqian, contracted gonorrhea.

On March 1, teachers at the Jinbeier Kindergarten, a private boarding kindergarten in Zhuzhou, Hunan province, found that the girl was ill.

An initial police probe ruled out foul play at the kindergarten after a mandatory screening of the school's 16 staff members found that none was a carrier of the disease.

The city's education authorities have ordered a probe into the cause of the disease, and they are cooperating with health authorities to determine if other children have also been infected.

Kang Naning, head of the kindergarten, said none of Qianqian's 40 classmates has shown symptoms of gonorrhea.

Meanwhile, the police investigation indicated that the girl was not sexually molested.

Qianqian's parents are migrant workers from rural Hunan.

Although she was staying at a boarding school, Qianqian left the school's premises after enrolling, and stayed with her aunt at a migrant workers' dorm at a local garment factory.

Qianqian's aunt was her primary caregiver until she was old enough to be checked into a full-time boarding kindergarten on Feb 13.

The girl's mother has only visited her once, but her aunt took Qianqian from the school on two Sundays to spend the night at the garment factory dorm.

Pupils play table tennis at Limin School, which enrolls children from migrant workers' families, in Jiaojiang district, Taizhou, Zhejiang province, in February. Huang Zongzhi / Xinhua