A mysterious disease has killed at least 12 people in Bangladesh and made many more sick and health experts said on Sunday they were sending samples to the United States for analysis.
Health authorities declined to comment on whether the sickness could be the bird flu that has broken out in several other parts of Asia, but a livestock official said there had been no reports of sick chickens.
"It is too early to comment on whether it is bird flu while the matter is still under investigation," said Abdul Faiz, a professor of medicine at Dhaka Medical College Hospital.
The disease has affected people in villages in Faridpur district, 150 km (94 miles) north of the capital, Dhaka.
Patients, most of them young boys, suffer from high fever, headache and vomiting before becoming unconscious. Some also suffered from diarrhoea, doctors said.
Three out of five patients admitted to the Dhaka Medical College Hospital with the symptoms had died in the past three days, doctors said.
Health officials and newspapers said nine others had died of the disease since January 17, most of them in Faridpur district.
"We are worried by the sudden spread of the mysterious disease and so far have not been able to identify it," said another Dhaka Medical College Hospital doctor who declined to be identified.
The government was taking steps to track the disease down, said Health Minister Khandakar Mosharraf Hossain.