Hundreds of reindeer crossing a frozen lake above Sweden"s Arctic Circle for their annual migration to winter grazing grounds drowned this week as the ice collapsed beneath them, according to Reuters. The herd of roughly 3,000 reindeer were being moved by their Sami herders from the western shore of the frozen lake Kutjaure to the east when some reindeer at the front suddenly turned back, causing the ice to crack and several hundreds to drown. "In the ensuing commotion the whole herd moved in circles, adding great pressure and weight on the ice," said Erik Gustavsson, a manager at the County Administrative Board of Norrbotten. The reindeer crashed through the ice and then trampled on each other as they tried to climb out of the water, he said. The indigenous Sami population live year-round in the harsh conditions of northern Sweden, Norway and Finland and are highly dependent on the reindeer for their livelihood. There are some 20,000 Swedish Sami who herd reindeer. Bertil Kielatis, chairman of the Sirges Sami village that owns the reindeer, told Reuters he had never seen anything similar in his lifetime and that there was no clear explanation as to why the herd hesistated to move forward. "Probably, they were fightened by something or felt worried," said Kielatis. Video on SVT"s website showed hundreds of carcasses lining the muddy shore of lake Kutjaure, which has been used for decades to transport the reindeer from their summer grazing fields to the "winterland", where they spend the winter months. On Friday, two helicopters assisted the herders with dragging the dead reindeer from the lake. Kielatis said because of the herd"s special breeding value, the economic loss could amount to hundreds of thousands of dollars. As it is too expensive to bury or transport the dead, their bodies will most likely be scattered in the surrounding wilderness, he said.