Marine wildlife experts were frantically trying to rescue some 140 pilot whales stranded on Thursday in the shallow waters of an estuary in the southwest of the state of Western Australia.

The whales are stranded at Toby Inlet in Geographe Bay, the Western Australia Department of Biodiversity, Conservation and Attractions said.

The area is near the town of Dunsborough in a region popular with tourists, and about 236 kilometres south of the state capital Perth.

“We understand there are four pods of up to 160 pilot whales in total spread across about 500 metres. Unfortunately, 26 whales that stranded on the beach have died,” a department spokesperson said in a statement.

“A team of experienced staff, including wildlife officers, marine scientists, veterinarians are on site or on their way.”

Based on previous strandings, “these events usually result in the beached animals having to be euthanised as the most humane outcome,” the spokesperson said.

Photos posted on Facebook by the state’s Parks and Wildlife agency showed a crowd of people near several beached whales.

Ian Wiese, from whale conservation group Geographe Marine Research, said more than 100 volunteers were at the scene.

“They were trying to comfort them and make sure that their heads were out of the water so they could breathe,” Wiese told Australian Broadcasting Corp television from the estuary.

In July last year, more than 50 pilot whales died after stranding on a remote Western Australia beach. The state experienced its largest whale stranding at Dunsborough in 1996 when 320 pilot whales beached themselves.

Pilot whales are known for their tight-knit social bonds, so when one gets into difficulty and strands, the rest often follow, according to the University of Western Australia.