Two archaeologists employed by Gotland county were dismayed to discover the valuables had vanished when they arrived at a field in Alva in Gotland to follow up on a recent find.
"It's just as saddening every time it happens because it's our heritage that disappears," said Majvor Östergren at the Gotland County Administrative Board.
The methodical thieves dug some 250 holes in a bid to secure as much booty as possible. Östergren estimated that the impostors had made off with 500 silver pieces worth a combined total of 250,000 to 500,000 kronor ($35,000 to $70,000).
Following the raid, the field was placed under police surveillance, enabling archaeologists to continue their excavation work, news website helagotland.se reports.
At a press conference on Monday county officials displayed some of the objects overlooked by the thieves, including 100 silver coins, a gold bracteate and a silver crucifix.