The pod of whales was found stranded in shallow water of an island near the northwest tip of Sumatra in Aceh Province, Whale Stranding Indonesia reported on its Facebook page.
WWF Indonesia confirmed 10 whales were stranded on Monday, seven of whom were returned to the water by Navy officials.
The nine whales were discovered in Ujung Kareng beach of Aceh Besar district at about 9:30 a.m. Monday, said Agus Salim, police chief at Masjid Raya sub-district.
'It is best to wait until high tide, but we are concerned they might die, ' Sapto Prabowo from the Natural Resource Conservation Agency said.
It is not exactly clear why whales and other marine mammals get stranded, but experts say it can be a combination of factors, from old age, illness or injury, to accidental navigation errors.
More than 250 of whales died as rescuers desperately attempted to return them to the water.