The carcass of a 20-metre-long blue whale washed ashore at Tamil Nadu's Valinokkam Beach in Ramanathapuram district on Sunday, officials said. The whale was aged about four-five years and weighed around 7-8 tonnes, said Keelakarai Forest Ranger S Sikkandar Batcha. Since the carcass was about a month old, the cause of death could not be ascertained, he added.