Young parents holding their children throng Shanghai's Beijing Road. For hours they have been waiting for an ultrasound check at the children's hospital to find out if their children, too, have developed kidney stones. They all fed their kids milk powder produced by the Sanlu company. 28-year-old Tang Ling has come with her 15-month-old daughter after hearing the news about China's latest food scandal.

"It all began in August", she recalls. "My daughter kept getting a high temperature. I had no idea what was going on. She had all the symptoms: She drank a lot of water, had pain when urinating, and her stool was like sand. At first, though, I didn't see any connection with the milk powder."

Tang Ling and her family were resettled to Shanghai after the Sichuan earth quake in June. The city administration provided milk powder, including the Sanlu variety, to all new arrivals with babies. When Tang Ling heard last week that milk powder in the market had been contaminated with melamine, a toxic chemical, she started getting worried and approached the local authorities -- who then referred her to the hospital.

Milk powder is popular

Almost every second Chinese mother feeds her new-born baby powdered milk. Fresh milk is considered to be highly contaminated, so most doctors recommend milk powder. Products of the Sanlu company used to be among the cheapest available and were therefore popular with migrant labourers and peasants -- such as the Yuan family from Hubei province. Two-year-old Tian Tian's father is also among those waiting in front of the Shanghai child clinic. Several other clinics had sent him away.

"I am number 300 on the waiting list here", the migrant labourer says. "This can take time. I came here in the morning from Putuo county. My son was never breastfed, we always fed him powder milk, and mostly Sanlu."

Little Tian Tian, too, is showing first symptoms of kidney stones. His father has taken time off from work to get him checked. He is the breadwinner of his family of three moving from one construction site to the next. He has no idea how to foot the medical bill:

"On TV they said all treatment was free. But even if the central government decides this, it doesn't mean it is applied everywhere. In all the big clinics here in Shanghai they haven't heard about it so far, it seems."

Angry parents

Meanwhile, people's anger is growing. Tens of thousands of parents all over the country have been to the hospitals with their kids. They are especially furious that the authorities seem to have known about the problem for months, but chose not to disclose the information and chose instead to risk the health of other babies. The first victim apparently was a five-month-old boy from Lanzhou city who died back on 1 May.

The Chinese health ministry admitted on Tuesday that the number of children developing kidney stones would probably rise further. About 1,200 cases had been discovered by Monday. 340 children are hospitalized, official sources said. Dozens of them are in a critical condition.