The red-and-white banners with the latest government propaganda fluttered above the grimy main street, warning farmers at an outdoor market about a substance that might not spring to mind as a dire menace: rat poison.

Yet the Chinese government regards the most lethal form of the poison, called Dushuqiang, very seriously. Since Oct. 1, anyone convicted of making, storing or selling the poison faces a prison sentence or even death. Government agents have raided illegal stocks and urged residents to hand over any private stashes.

''Stamp Out Dushuqiang, the tumor threatening people's lives,'' declared one of the banners. Another banner prodded, ''If there is Dushuqiang at home, please hand it over and you will rest assured.''

All the government interest raises the obvious question: why?

The answer is that in a country where private gun ownership is prohibited and where serious violent crime is considered rare, Dushuqiang has become a murder weapon. In a high-profile case on Oct. 21 in this mountainous region of Hubei Province in central China, officials say a woman killed 10 guests at her husband's funeral banquet by sprinkling poison on the food.