Archaeologists near Blenheim have discovered what is believed to be one of the oldest building sites in the country.

The team, led by Otago University Associate Professor Richard Walter, is carrying out a month-long survey and excavation at the Wairau Bar. The project will also involve the reburial of the remains of the area's first settlers which were taken for study more than 50 years ago.

A spokesperson at the site says the archaeologists have also discovered an area of soil which looks to be the remains of a 700-year-old building.