A burial vault was uncovered by a water main project at Washington Square Park, city officials said. View Full Caption Department of Design and Construction

GREENWICH VILLAGE — Workers on a water main project at Washington Square Park have uncovered a burial vault that could be as ancient as the century-old infrastructure they're upgrading, officials said.

The vault is believed to date back to the 19th century, officials said, but further investigation by archaeologists and anthropologists is needed to determine its significance and its contents.

► UPDATE: ARCHAEOLOGIST DETERMINES BURIAL VAULTS BELONGED TO ONE OF TWO CHURCHES

The project is located just east of the park, which was built on top of an old burial ground for the poor known as a "potters field." The park is just one of many known hidden burial grounds in New York City.

The workers were in the process of a longterm Department of Design and Construction project that involves the installation of catch basins, sewer manholes, and traffic lights. The roadways above will be restored with a green bicycle lane, new street signage and private utilities in the area will be upgraded, officials said.

The DDC commissioner said the agency is "re-designing the work to accommodate findings of importance."

"Working together with the Landmarks Preservation Commission, DDC will evaluate the extent and significance of the vault and its contents," Commissioner Feniosky Peña-Mora said in a statement.

The agency is continuing work on the project as planned south of the burial vault, which is on Washington Square Park East near Waverly Place.

The vault area itself is being blocked off, limiting pedestrian and vehicle traffic until archeologists and anthropologists can complete their study of the find, the agency said.