(CNN)Rescue teams in Tasmania were already frantically working this week to save about 270 pilot whales stranded in a harbor. Up to a third of the animals were believed to be already dead, with the clock ticking to save those still alive.
Tasmania finds another 200 pilot whales that may all be dead in mass stranding
Then, on Wednesday, they found another 200 stranded whales, which they fear may also be dead -- making this the largest mass whale stranding in the Australian island state's history.
Tasmanian authorities spotted the first batch on Monday: the estimated 270 whales were stranded in the small town of Strahan, scattered along two sandbars and the strip of beach. After determining that about a third had died, officials, volunteers and marine experts launched a concerted rescue mission on Tuesday.
Wednesday brought new horrors, after aerial surveying detected a second group of 200 whales further south in Macquarie Harbour, believed to be part of the same mass stranding event at Strahan.
"From the air most of the additional whales detected appear to be dead, but a boat has headed over there this morning to do an assessment from the water," said Nic Deka, regional manager of Tasmania's wildlife service, in a press release.
This brings the total number of whales for the mass stranding to more than 450, according to the Department of Primary Industries, Parks, Water and Environment.
The additional whales were found in a part of the harbor where the water is a dark tannin color -- so they may have been stranded, washed back into the water, then back into the bay, making them more