Dr Bunnam Chaiwisut, head of the provincial public-health office, said the three people now showed negative after a blood test but were still under observation, one of them in hospital and two at home.

He said the infectious bacterial disease did not spread from human to human and called on the public not to drink fresh or unpasteurised goat's milk.

Blood tests have been conducted on another 24 people, all goat-breeders or their relatives living in tambons Nong Bua and Tha Makham, and results will be available soon, said the doctor.

An official at the livestock office said experts on animal disease were away on an administrative trip. When asked if he could provide any details, the official said he was not aware of brucellosis in the province.

Goat-breeder Vitthaya Reethae said the livestock office had told him to wait for vaccine after he notified it several weeks ago that a large number of his goats had died and the females miscarried.

When vaccine was provided, he injected his goats, but miscarriages continued, said Vitthaya.

A medical worker from the public-health office collected blood samples on Wednesday from Vitthaya, some of his relatives and a family in tambon Nong Bua, where 56 goats had been put down by livestock officials.