XIAMEN, China — Perched on stools, four workers stuff freshly made noodles into plastic bags on the ground floor of the two-story Lin family home. A black-and-white mutt wanders lazily around their feet. Flies circle and land at will.

Bags and basins cover almost every inch of a concrete floor that is partly damp, partly sticky with dough. Weak sunshine through the front door provides the only light in the sweltering room.

These noodles aren't exported; they're only sold locally. But the hidden and unregulated nature of the Lins' business — and countless others like it — helps to explain why China is caught in a food crisis.

"We're not allowed to apply for a permit to make food because this is our home, and we're not supposed to work out of it," says Lin, who squeezes out a living through his illegal noodle business, nestled in a dusty warren of workshops and residences on the edge of this port city of 1.6 million.

"Of course we can't meet national food-safety standards," says his wife, Chen. They would not give their full names and fear talking with reporters. If anyone finds out, she adds, "my family will starve."

China faces an uphill battle as it rushes to fix its regulatory system amid a raft of disclosures of tainted exports to the U.S. and other major markets.

"It is becoming increasingly urgent to raise the food-safety standards to international levels," the state-run China Daily newspaper editorialized recently.

China's reputation has collapsed in recent months since deadly toxins and dangerously high levels of chemicals were found in exports ranging from frozen fish to pet food.

The discovery of diethylene glycol, a thickening agent in antifreeze, as a cheap sweetener in Chinese-made toothpaste has resulted in bans in Asia and North and South America. On Friday, U.S. regulators ordered a recall of more Chinese-made products deemed dangerous to children: jewelry decorated with lead paint, and building sets with small parts that pose a choking hazard.

"It was bound to happen sooner or later," said Michael F. Moriarty, vice president of A.T. Kearney, a Chicago-based consulting firm that recently put the cost of fixing China's food-safety system at $100 billion.

"China is a very entrepreneurial supply market, and enthusiasm sometimes outweighs prudence," he said.

The world's most-populous country is awash in tiny mom-and-pop operations. Chinese authorities announced last month that they had closed 180 food factories since December after inspectors found formaldehyde, illegal dyes and industrial wax being used to make candy, pickles, crackers and seafood. All had fewer than 10 employees.

Another regulating agency said it shut 152,000 unlicensed food producers and retailers last year for making and selling fake and low-quality products.

But new ones keep popping up. About three-quarters of the country's million or so registered food-processing plants are small and privately owned, according to the China Daily. That doesn't include the unregistered ones.

"The big issue is that there are a lot of small manufacturers," said Yang Dali, director of the East Asian Institute at the National University of Singapore and author of a paper on the politics of food safety in China. "Sometimes they may be more eager to make a quick buck, and that makes the situation worse because they don't care about their reputation."

The most distinguishing feature of China's central food-safety regulatory system is that there isn't one. Responsibility is split among at least six agencies, including those that handle health, agriculture and commerce. The lines of authority are ill-defined, and different bodies oversee different laws.

"Things fall through," said Philippa Kelly, a Beijing-based consultant who works with the Chinese government on food-safety issues.

A report released last week by the World Health Organization, the Asian Development Bank and China's State Food and Drug Administration condemned the fragmentation, saying it was "confusing and greater clarity was urgently needed."

"This lack of clearly assigned responsibility leads to a situation where no agency or authority can be properly held accountable for their action or inaction," the report said.

Adding to the problem is rampant corruption. Officials can be bribed, and instead of shutting down illegal operations, many regulators just impose fines so they can collect more money in the future, Yang said.

Chinese officials insist that exports are safe, though they also have called for stricter inspections and threatened violators with punishment in an apparent effort to reassure international customers.

"Ninety-nine percent of food exported to the United States was up to safety standards over the past two years, which is a very high percentage," says Li Yuanping, a Chinese official in charge of imported and exported food safety.

Exports are subject to tighter specifications and multiple checks by authorities both in China and importing countries. But there are gaps, Yang said, because "regulatory agencies are often short on staff and funds in various localities and cannot fully police the manufacturers."

Some companies do it right.

Amid the banana trees and industrial parks on the outskirts of Xiamen, Donghai Frozen Foods Co. Ltd. learned the price of failing to keep up with international standards.

Two years ago, it had to discard 2,000 tons of edamame because they did not meet new Japanese pesticide regulations that had come into effect after the soybeans were processed.

Donghai, which has 300 food-handling employees, ships 7,000 to 15,000 tons of frozen vegetables a year, mainly to Japan, the United States and Australia.

On a recent afternoon, soybeans arrived by the sack from the company's fields and were briskly unloaded by workers.

In an airy building, two women in white facemasks filled a huge metal steamer with crates full of cleaned pods. Others poured cooked beans into crates of ice for cooling. Anything that dropped on the floor was discarded.

Guo Mingfeng, head of administrative affairs at the Taiwanese-owned company, said five to 10 self-inspections are performed during processing and more checks are done by China and the importing country.

"We know what happens from field to factory," he said. "We have full control of the process."

Ultimately, experts say, the answer to China's woes lies in efforts like Donghai's.

"Food or indeed any other product is not really improved by legislation or government control," said John Chapple, who heads Sinoanalytica, a food analysis laboratory in the coastal Chinese city of Qingdao. "It is improved because the people producing it see the commercial benefit in making it happen."

The problem, he said, is that despite exceptions such as Donghai, "it's not happening in China yet."