Iceland resumed commercial whaling in 2006.
Dr Phillip Clapham, one of the world's leading experts on large whales from the NOAA Alaska Fisheries Science Centre, agreed it was a blue whale photographed at the whaling station.
"They go after it as a fin whale".
"There is nearly no possibility that an experienced observer would have misidentified it as anything else at sea".
"To mistake a blue whale for a fin whale is impossible, this whale has all the characterisations of a fin whale in the ocean".
"Whale 22 (documented by us on July 7th midnight / July 8th early morning) shows features of a blue whale (darker belly, all black baleen, bluish colour)", they wrote in a Facebook post.
It is believed there are maximum of 25,000 blue whales in the world and only five hybrids have been in identified in Iceland since 1986.
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A change in Japanese regulations caused the Icelandic government to reconsider their moratorium on whaling, as Loftsson's company kills fin whales predominantly for export to the Japanese market.
Icelandic whaling company Hvalur hf who recently began hunting fin whales again, may have killed a rare, protected blue whale or a blue whale/ fin whale hybrid.
Sea Shepherd, an global anti-whaling organization, condemned the Icelandic whaling company Hvalur hf on July 11, claiming they illegally slaughtered an endangered blue whale.
Sea Sheperd said it was the 22nd whale killed by Loftsson's outfit in the past three weeks, the others being endangered fin whales.
Sea Shepherd UK's Chief Operating officer Robert Read demanded that DNA samples should be taken from from all the whale meat and parts in storage at Loftsson's whaling station and warehouses. He said: "I have viewed plenty of Blue whales on the surface, dived with them beneath the surface in West Australia, off the coast of California, in the Southern Ocean and in the waters off Newfoundland". Simmonds, said: "This bad incident comes as Japan is rumoured to be planning an attempt to overturn the global moratorium on commercial whaling, and clearly speaks to how utterly inappropriate it is for countries to even contemplate allowing a large-scale return to this grossly inhumane and haphazard industry".
Experts claim it is a blue whale, a protected species which has not been harpooned by anyone for the last fifty years.
Mr Loftsson said his crew spent an hour observing the whale before shooting it, and that they have never mistakenly taken a blue whale. Before the commercial whaling of the 20th century there were about quarter of a million blue whales.