"The area is currently closed to the public because of the risk from whales exploding," the conservation department said in a statement.

Workers in protective clothing would spend the day cutting holes in the whale carcasses, "like popping balloons" with knives and two metre (six feet) needles, to release internal gases that build up pressure, a DOC spokesman told local radio.

It would take several months for the bodies to decompose and turn into skeletons.

The surviving whales were last seen swimming six kilometres (four miles) offshore on Sunday evening, according to DOC.

Last Thursday a pod of about 400 whales became stranded, with a second pod of more than 200 whales stranded on Saturday.