LONDON - Archaeologists conducting a major excavation at England's Stonehenge said they had made a key breakthrough that may help explain why the site was built, the BBC said Wednesday.

According to the broadcaster, which is funding the dig as part of a special programme to be broadcast in the autumn, the team of archaeologists has reached a series of sockets that once held bluestones, smaller stones, most of which are now missing, that made up Stonehenge's original structure.

The bluestones were transported from hills in Wales, some 250 kilometres (155 miles) away, and the researchers think they were brought to the iconic site on Salisbury Plain in Wiltshire, west England, because ancient people believed they had healing properties.



"The first week has gone really well," Professor Time Darvill, one of the academics leading the excavation, was quoted as saying on the BBC website.

"We have broken through to these key features. It is a slow process but at the moment everything is going exactly to plan."

As part of the two-week dig which started March 31, the first inside the stone circle since 1964, the archaeologists must now extract organic material from the holes left by the bluestones to better date when they first arrived.

During the excavation, the researchers have also found a beaker pottery fragment, Roman ceramics and ancient stone hammers.