A mysterious new disease has begun killing chickens and striking swine in the United States, with a suspected culprit so common that some researchers simply cannot believe it, according to a report in next week's issue of Science magazine.

The outbreak of the disease, first reported when it struck chickens in Arizona several years ago, is believed to have caused hundreds of other illnesses and deaths among chickens and swine in the United States, according to Pat Hamilton of the poultry science department of North Carolina State University.

Meanwhile, in Arizona, an egg company whose chickens contracted the disease has sued the company that sold it the feed suspected of causing the illness. The feed company has sued in return, and the growers of the corn that went into the feed have sued the feed company. Two other large feed and poultry companies were brought into the tangle of suits to buttress one side or another.

The tale began several years ago in Arizona, when chickens on that state's biggest egg farm fell ill and began dying with no apparent cause.

After lengthy investigation, the outbreak of the illness was traced to the chickens' corn feed. But researchers disagree, partly because the suspected culprit in the feed seems so unlikely:

Recent research suggests that it may have been the most common of all things that grow on corn, a fungus so prevalent in kernels that researchers say it is very difficult to find corn that does not have it.

Recent research at several laboratories in the United States and South Africa have shown that the common fungus, Fusarium moniliforme, can produce lethal poisons despite its innocuous reputation. Research also shows that feed with high levels of the fungus can cause illness and death.

But the crucial direct connection has not yet been made between moniliforme and the illnesses. Researchers have tested mold-contaminated corn samples for at least 16 different toxins, but have not found the active one.