A Stone Age archaeological site in the heart of Breckland could be larger than originally thought following the discovery of flint nearby.

A series of test pits in an area clsoe to to Grimes Graves, an established Neolithic flint mine, were dug on two separate occasions and the pieces were discovered.

The struck flint could indicate the area was bigger than first thought, and while it does not necessarily mean there are new mines to discover, could indicate a larger area of archaeological interest.

Anne Mason, spokesman for the Breckland Society, which organised the digs on behalf of Cambridge-based PhD student Barry Bishop, said around 42 volunteers arrived for the first in February and around 35 at the second this month.

She said the survey was 'highly important' in adding to the knowledge of Neolithic flint mining in Breckland. The time of year was chosen because harvesting had cleared the area of trees.

'It's absolutely fantastic,' she said. 'Everybody said how much they had enjoyed it. We can only do the two at the moment because of nesting woodlark and other birds but they were very successful.'

A number of struck flint shards were found on site, as well as a fragment of late Neolithic pottery identified by one of the volunteers.

Mrs Mason added: 'It looked like a little pebble with charcoal on it and it shows there was important human occupation and that Neolithic people were on the site.

'All the time we're adding to the knowledge of the main Neolithic sites in Norfolk and our knowledge of Grimes Graves itself. We've learnt there may be a larger area than we first thought.

'Now, as other areas are found and exposed, we can do some work because we have this amazing database of people who are interested in volunteering.'

The area is already home to a series of flint mines which are open for public viewing and is a site of special scientific interest (SSI).

The 400 pits was first named Grime's Graves by the Anglo-Saxons but it was not until one of them was excavated in 1870 that they were identified as flint mines dug more than 5,000 years ago.

Nearby, the current groups excavated 31 test pits in the sandy soil at 50 metre intervals at a depth of one metre. The aim was to increase knowledge of any archaeological remains in the survey site. The struck flint will now be taken away to be washed and processed.

By finding out what was on the site the remains can now be protected during tree planting in the winter.