By John Acher

COPENHAGEN (Reuters) - Danish archaeologists said on Tuesday they had re-opened a mass grave of scores of slaughtered Iron Age warriors to find new clues about their fate and the bloody practices of Germanic tribes on the edge of the Roman Empire.

Bones of around 200 soldiers have already been found preserved in a peat bog near the village of Alken on Denmark's Jutland peninsula.

Experts started digging again on Monday, saying they expected to find more bodies dating back 2,000 years to around the time of Christ.

"I guess we will end up with a scale that is much larger than the 200 that we have at present," Aarhus University archaeologist Mads Kahler Holst told Reuters.

"We have only touched upon a very small part of what we expect to be there ... We have not seen anything like this before in Denmark, but it is quite extraordinary even in a European perspective," he added, speaking by phone from the site on damp grazing meadows near Jutland's large lake of Mossoe.

The first bones, belonging to people as young as 13, were discovered in 2009. Cuts and slashes on the skeletons showed they had died violently, said Holst. But nothing was known for sure about the identity of the killers, or their victims.

"That is one of the big mysteries ... We don't know if it is local or foreign - we would expect it to be local," Holst said.

"We think it is a sacrifice related to warfare and probably the defeated soldiers were killed and thrown into the lake," he said.

The remains are from the beginning of the Roman Iron Age, though Roman armies never reached so far north.

"It was the time when the Roman Empire had its greatest expansion to the north," Holst said. But even that push only got the Romans as far as modern day Germany, a few hundred kilometers to the south of the Danish site.

"This conflict could have been a consequence of the Roman expansion, its effect on the Germanic world," Holst said. Continued...