SOUTH RIVER, N.J. (CBSNewYork) – An unmarked mass burial ground has been found at a cemetery in Middlesex county.

Residents have long believed it was there, and say it is linked to one of the worst epidemics in human history.

Next to 100-year-old gravestones in South River lies a mystery. Local legend says a piece of land in the southeast corner of Washington Monument Cemetery contains victims of the 1918 influenza epidemic.

Now science may have proven that to be true.

“We wanted to put this to the test and commissioned a ground penetrating radar survey,” said Mark Nonestied with the Middlesex County Office of Arts and History. “Rather stunned to find 400 unmarked burials.”

More than 50 million people worldwide died during the 1918 flu epidemic.

“South River, like many areas in Middlesex County, were placed in quarantine at the height of it, closing schools, factories trying to contain it,” Nonestied told CBS2’s Meg Baker.

A photo from the time shows a beer wagon carting a coffin to the cemetery. The caption reads “The demand for caskets kept carpenters busy 24 hours a day.”

A local newspaper article, entitled “Death of an Infant,” describes how a mother lost her baby a few days after burying her 18-year-old son while also fighting for her life.

“The town is over 250 years old. Back in 1918, it would have been a very blue collar town, many poor people who couldn’t afford to have an official burial,” said South River Mayor John Krenzel. “Also at the time, panic going on, flu killing so many, so fast… had to dispose of bodies.”

Thomas Howley, a trustee of the cemetery, grew up in the town hearing the tales of old.

“If you wanted to have a pauper’s field, it would be in the outback,” he said.

The burial records for the cemetery were lost years ago, so historians need help from families who may have more information about the immigrants from many lands who lived there.

“Hungarian and Russian, the cultural makeup who lived and worked in factories and were buried here,” Nonestied said.

The next push is to place a historical marker to commemorate those that lost their lives.

The survey shows both adults and children were buried in that section.

Historians aren’t sure if all the burials are from 1918, but say there is enough evidence to suggest many victims ended up there.