Tunnels run beneath Chinatown in Fresno, Calif.: brick-walled passages that were once home to people and activities that couldn't be mentioned aboveground....

Now, a group of archaeologists is using ground-penetrating radar to find evidence of the secret passages, which are believed to branch out from long-abandoned basements littered with animal and human waste, cobwebs and other filth.

The project, funded by the city and headed by a group working to preserve Chinatown, will take data gathered via radar and compare the findings to the memories of those who recall the neighborhood's heyday, said Kathy Omachi, vice president of Chinatown Revitalization. That will help archeologists decide where to dig trenches and look for the passages, researchers said.