A mass stranding of long-finned pilot whales in southwestern Australia led to the deaths of 29 of the beached creatures on Thursday, officials said. Another 100 or so of the whales were rescued and redirected out to sea from Toby’s Inlet, which is at the lower tip of Western Australia, about 150 miles from Perth, the state capital.

Images released Thursday by Western Australia’s Parks and Wildlife Service showed a large group of pilot whales crowded together at the edge of the Toby’s Inlet shoreline, where the ocean meets the land. Although many were still submerged in the very shallow water, several of the whales were fully beached.

Wildlife officers, marine scientists and veterinarians were deployed to the site. Just before noon, the parks and wildlife service reported that four pods of as many as 160 pilot whales were stranded in the water and spread across an area of roughly 1,600 feet, with 26 whales stranded on the beach itself.

“Our team is making every effort to safely respond and keep volunteers and staff safe, while also acting in the best interests of the whales,” the wildlife service said as they worked to manage the situation. “Our team is assessing the conditions of the whales that have stranded on the beach. Our teams on the water are trying to keep the animals together and away from the beach.”

Officials said originally that the beached whales would likely need to be euthanized, based on previous similar incidents. Last July, dozens of whales belonging to the same species died on a different beach in Western Australia after becoming stranded. In the end, the wildlife service said that 51 whales had died of the 96 that were stranded.

Ian Wiese, a whale researcher, was one of hundreds of volunteers that helped wildlife officials carry out their rescue operation, the Associated Press reported.

“When I first arrived, there was, I think, 160 in the water — almost out of the water — and there were a couple of hundred people who were with the whales, they were trying to comfort them and make sure that their heads were out of the water so they could breathe. And then after an hour or so, all of a sudden the ones that were in the water that were still alive left and went out to sea,” Weise told the AP.

“They may well decide to come back to shore somewhere on another beach nearby or something — that often happens, but we’re hopeful that they won’t,” he said.

In the wildlife service’s final update Thursday, Pia Courtis, a regional wildlife officer, confirmed that the larger group of rescued whales had been routed out to sea. A “spotter plane” surveyed the area but did not see those pods during the flight, which Courtis suggested could be a promising sign.

“There has been no further sightings of the pod this afternoon, which is good news,” Courtis said. “The spotter plane will continue to monitor the area during daylight hours, but we are hopeful that the pod will not return to the shallower water.”

The dead pilot whales were being removed from the beach when Courtis gave that last update. The wildlife officer said they would collect measurements and some samples to biopsy from the animals before moving them to a landfill. Courtis said the hope is that information taken from carcasses will help scientists understand this species better, and the pod specifically, to hopefully gain insight into why they were stranded.

Long-finned pilot whales are a large species of dolphin, with individuals usually measuring between 19 and 25 feet in length and weighing between 2,900 and 5,000 pounds, according to the National Oceanic and Atmospheric Administration. A pilot whale’s typical lifespan is anywhere from 35 to 60 years, although their survival is threatened by several factors including chemical contaminants, disease, entanglement in fishing gear and ocean noise. They tend to travel in dense pods, and much of what is known about the species and their behaviors has come out of other mass strandings. 

Reasons behind whales and dolphins becoming stranded or beaching themselves are not always clear. Depending on the scenario, scientists and experts have posited in the past that injury or illness of one or more animals in a given pod could contribute to the phenomenon, as well as unusual weather and attempts to escape underwater dangers like entanglements.