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

Rick Lew knows, because he walked the passages as a child, entering through a trapdoor in his grandfather's liquor store.

"There was a nightlife you couldn't see from the streets," he said.

But to many others, the lace-work of tunnels sprawling under the city was just another tall tale from Fresno's days as a Western railroad town and a hub of gambling and prostitution.

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.

The approximately six blocks just west of the railroad tracks that make up the historic Chinatown were Fresno's birthplace, said Karana Hattersley-Drayton, the city's historic preservation officer. Unlike the better-known Chinese quarters of San Francisco and New York, there's little left of it today — at least on the surface.

But fire insurance maps from the 1880s show a densely populated area offering a stark contrast from the wide-open ranch and farm country all around.

It was home to the Chinese laborers who laid Fresno's foundations, and to successive layers of immigrants — Japanese, Armenians, Mexicans, Portuguese, Basque and others — who were kept separate from the growing white population by the iron boundary of the train tracks.

The area long housed family run stores, temples, churches, Chinese and Japanese schools. But it was also host to illicit activities — gambling, drinking during Prohibition, and prostitution — not deemed respectable enough for the "good side of town."

Omachi's father, a Japanese immigrant, was born here in 1913 "between a bar and a house of ill repute," she said.

Many establishments had basements, some of them interconnected. Of those that can still be seen today, some end in bricked-off walls that longtime residents say hide tunnel entrances.

As late as the 1950s, when Lew was a boy, Chinatown was still thriving — both its respectable establishments and as its shadier side.

He remembers visiting the underground world with his father, first passing though a dark basement before descending into a lit tunnel with an arched roof and enough space for two people to pass by each other. There were people there he recognized from the neighborhood. And then there were the glamorous women whose images remain seared in his memory decades later.

"They were off to the side, in bright satin dresses, one red, one blue," said Lew, speculating that they were probably prostitutes. "I later asked my father about it. He said it was something we don't mention."

Jon Brady, lead archaeologist on the project, said the tunnels may have been built to provide cool underground storage in a region known for sweltering summer heat. But they later proved handy for communication, transportation, and even escape when necessary.

"These groups that lived on the fringe could have resorted to them to protect themselves, communicate away from public view, who knows what else," Brady said.

Local lore holds, though it still hasn't been proved by research, that a tunnel one time extended beyond the railroad tracks into the traditionally white part of town, possibly allowing "respectable" citizens access to the illicit charms of Chinatown.

"Some say that was blown up during prohibition," said Hattersley-Drayton, who got a lot of calls from longtime residents once the project got started. "I'm hearing that from a lot of people, but we just don't know yet."

In the 1950s and '60s, many of Chinatown's buildings were torn down to make way for new development or freeways, and much of the history was buried, Lew said.

"Many of the older residents packed up and left, and it started getting rough," Lew said. He now lives far from Chinatown, but remains surrounded by artifacts from the days his family was an important part of the neighborhood: tall, elaborately decorated vases, paintings and sculptures handed down by his grandfather, and the old manual cash register that rang up purchases at the liquor store.

Today, Fresno's Chinatown is largely abandoned, peopled by the homeless, with many of its facades boarded up and only a few remaining businesses — an herb shop, a fish market — serving as evidence of the lively commercial center and night spot it once was.

It's a part of the region's history that's been forgotten, but that was an important aspect of the city's development, and of the settlement of the West, researchers said.

"This is an opportunity for us to look at where we were," said Patti Miller, spokeswoman for the city. "As we turn our eyes to revitalizing downtown, this aspect is critical."

Although the archaeological study is just beginning, there appears to be some evidence of underground "linear structures" that could be large drainage pipes, or tunnels, said Brady.

Hattersley-Drayton hopes someday Chinatown and its excavated tunnels might be developed for heritage tourism, bringing some income to what is now an impoverished area.

For now, it's just about understanding what's there, Brady said.

"This is a first step, and it's about approaching parts of community history that are not in books," said Brady. "Parts that are literally below the surface, but that deserve to be told."