XINXING, China (AP) — Heartbroken at the sudden death of their baby boy, the Yi family struggled to forget what they thought was a tragic twist of fate. They burned his clothes, toys, everything but a single photo and the baby formula he drank.

Then health officials suddenly arrived at the family's rural home last month with shocking news: Milk contaminated by an industrial chemical might have killed their son. On Monday, the Yis filed a lawsuit against the company at the heart of the scandal — the first court action by a family of a child who died.

Unrecognized at the time, 6-month-old Yi Kaixuan's death in May made him among the first victims in what would become a nationwide scandal. It would be another four months before the dairy, Sanlu Group Co., revealed there was a problem, and the government later confirmed there was widespread contamination of China's milk supply. Four infants have died and tens of thousands of children were sickened.

"I have no idea how any of this happened," Yi Yongsheng, the baby's slight, soft-spoken father, told The Associated Press on Sunday as he ran his fingers through his hair.

His wife, Jiao Hongfang, crouched outside in the courtyard cooking silently. She had collapsed in grief at her son's death and again in September when officials came with news of the tainted milk.

"She doesn't want to face this anymore," Yi said.

The scandal is one of the worst tainted food crises in China in years. It has exposed shoddy practices in the booming dairy industry and raised questions about when the government first knew dairy products were contaminated with melamine, a chemical used in making plastics and fertilizers. Unscrupulous suppliers are suspected of adding it to watered-down milk to mask the resulting protein deficiency in quality tests.

Sanlu — a state-owned company whose products were the most heavily tainted — is now largely defunct, with the Xinhua News Agency reporting Monday that several other companies were vying to scoop up its assets.

Worst affected, however, have been China's poor, who turned to Sanlu products because they were less expensive.

In places like Xinxing, a town of brick and packed-earth houses surrounded by corn fields in the roughly terraced hills of western China, families have little. Yi spends most of the year working construction jobs in one of China's largest cities, Xi'an, while Jiao tends their small plot of land. The family makes about $580 a year.

The baby boy was their second child; they have a 5-year-old daughter. China's strict family planning rules allow many rural Chinese to have a second child in order to try for a boy, in a nod to traditional preferences for male heirs.

Infant formula for the baby was expensive but necessary. Jiao's breast milk wasn't enough, Yi said, so they started supplementing with milk powder. By his second month, formula was all the infant was fed. They thought the formula was healthy, and Sanlu was a brand with a good reputation.

"And it was just a little cheaper than the others," Yi said — $2.60 for a package that would last three or four days.

But on April 20, the baby wouldn't stop crying and had problems urinating. Jiao took him to the village clinic, but they couldn't pinpoint a problem.

Alarmed, Yi left his construction job and returned home. The family headed for the Gansu provincial capital, Lanzhou. On April 30, they took the baby to two city hospitals. Doctors were stunned, Yi said. They said they'd never seen a child with so many kidney stones, and the situation was critical.

A frenzy of testing followed, and the bills piled up past $145. The parents didn't sleep all night, waiting.

Around noon the next day, a doctor came to tell them their baby had died.

No one at the time, the doctors included, seemed to link the kidney stones and the infant formula.

Terrible luck, the family decided. In keeping with local custom that treats the death of a child so young as a tragedy best quickly forgotten, they burned everything. They kept a single photo of the child — shown with his grandfather during Chinese New Year in February — and the infant formula. It was a luxury and could be used for another child. There was no funeral.

"Burning those things was like walking away," Yi said. "To keep looking at them and remembering would be too sad."

The family did their best to forget the boy, until Gansu provincial health officials arrived in mid-September. They asked many questions and took samples of the baby formula, then told the family to wait — they would call later with information.

Since then, the family hasn't heard a word.

The Gansu provincial health department declined comment, its spokesman saying they do not give telephone interviews.

Yi only considered undertaking legal action after a friend contacted a Shanghai-based lawyer who'd grown up in the nearby city of Tianshui.

Attorney Dong Junming took the case without charge and started adding up the damages: $6,700, which Dong estimates equals 20 years of the average Gansu farmer's salary; $146,000 for emotional damages.

"Frankly? Sanlu won't pay out that much," Dong said Sunday at a cafe in Lanzhou, where he was making final preparations for filing the lawsuit. "But we think this situation is really shocking, so we're going to ask."

Such liability suits are rare in China, despite growing public awareness of an individual's legal rights. A group of some 100 lawyers who offered free legal advice to victims of the tainted milk scandal have faced official pressure to withdraw from the cases, attorney Chang Boyang told the AP. After the massive earthquake in May, some parents whose children died in the collapse of shoddily built schools said they were offered cash in return for signing pledges not to sue.

So far, just two other known lawsuits have been filed in the tainted milk scandal, both by families of babies who were sickened but survived. In both — one in southern Guangdong province, the other in central Henan — it is not clear whether the courts will accept the lawsuits. In the Yis' case, Dong said he was told the court would make a decision Tuesday.

In Xinxing, Yi is relying on Dong to handle the legal details. He studied no further than ninth grade, and Jiao only went to primary school. They had placed their future in their children.

Both Yi and his wife are only 30, and Yi said some day they might try for another child, a sibling for their daughter.

The girl, Yi Xuan, really liked her baby brother, Yi said. "But maybe she's already forgotten him."

Yi sat on a low stool as he spoke, the single photo of the baby on a table beside him. The daughter, pink-cheeked and shy, hid behind him but eventually noticed the photo. She smiled and said the baby's name.

She reached for the photo. But Yi looked hard at her and pushed it away.