By Subir Bhaumik
BBC News, Calcutta
Six aboriginal tribespeople in India's eastern Andamans archipelago have died after mistaking a toxic chemical that washed on to their shore for alcohol.
Fifteen more Onge tribespeople, who number only about 100, have also fallen sick after drinking the chemical.
The Andaman administration has flown a medical team to Dugong Creek, in the southern Andamans, where the Onge live.
Many Andamans tribes are endangered and attempts to reduce contact with settlers have not always succeeded.
The medical team is headed by Ratan Chandra Kar, deputy director of health services.
He said: "We are trying to save as many Onges as possible. This is a great tragedy."
Police superintendent of the South Andamans district, Ashok Chand, told the BBC: "The Onge tribals drank the chemical mistaking it to be alcohol last night from a plastic can that washed ashore from the Bay of Bengal at Dugong Creek."
The helicopter that carried the doctors to Dugong Creek is being used to fly back critically ill Onges to the Andamans capital, Port Blair, where medical services are better organised.
Environmentalists and anthropologists have blamed the administration for its "insensitivity" to the tribespeople.
The Jarawas are one of a number of at-risk tribespeople (Photo: Pankaj Seksaria)
"Time and again, we have asked the administration to reduce contact between the aboriginals and the settlers. But that has not happened and the aboriginals have picked up dangerous habits like alcoholism," said Sita Venkateswar, author of a book on the Andaman aboriginals.
With the death of the six Onge tribesmen, the population is now just 94 - down from 672 in 1901.
Some of the other tribes like the Great Andamanese are almost extinct.
The Jarawas number a few hundred but they have come under threat from settlers because the Andaman trunk road passes through their habitat.
In recent weeks, Jarawas have attacked and killed encroaching settlers while at least one Jarawa has been killed by them.