Archaeologists on Monday began a fresh excavation on Stonehenge, which they claim could unravel some of the site’s ancient mysteries.

The two-week excavation, the first inside the famous stone circle for almost 50 years, will search for the bluestones that were used to build the site’s first stone structure 4,500 years ago.

They formed a small circle that predated the mysteriously aligned, free-standing giant sarsen stones erected later, which make up one of the world’s most famous landmarks.

The team of archaeologists, led by Tim Darvill, a professor at the University of Bournemouth, and Geoffrey Wainwright, president of the Society of Antiquaries, hope that radiocarbon dating of the circle’s fragments will yield clues to the precise nature of the site.

The excavation is going ahead with the special consent of English Heritage, the conservation group, and Andy Burnham, the culture secretary. Simon Thurley, chief executive of English Heritage, said: “The bluestones hold the key to understanding the purpose and meaning of Stonehenge.

“Their arrival marked a turning point in [its] history, changing the site from being a fairly standard formative henge with timber structures and occasional use for burial, to the complex stone structure whose remains dominate the site today.”

Professor Darvill described the dig as “an incredibly exciting moment and a great privilege”.

“This excavation is the first opportunity in nearly half a century to bring the power of modern scientific archaeology to bear on a problem that has taxed the minds of travellers, antiquaries, and archaeologists since medieval times.”

Scientists have struggled to formulate a theory as to why the bluestones that were used in Stonehenge’s earliest structures were transported 150 miles from the Preseli Hills in south-west Wales to their present location on Salisbury Plain.

Some of the burials excavated around Stonehenge show a good proportion of people who had undergone operations to the skull, or had walked with a limp, or had broken bones. That has led the project team to surmise that Stonehenge was a centre for healing.

During the current excavation, Stonehenge will be open as normal and visitors will be able to observe latest developments live on plasma screens.