The province was declared a bird-flu outbreak zone on Thursday after tests confirmed fowl had been infected.

Many migratory birds frequent the Central province.

Angthong livestock chief Surachon Tangwiwat suspects that pigeons and Asian openbill storks living in the province could have spread the flu.

He said livestock officials had taken preventative measures since receiving reports of fowl deaths in Samko between January 21 and January 23.

"I immediately went there to meet local people and ask them to agree to the culling. Then, specimens were collected and sent for lab tests," Surachon said. "We are confident we will be able to prevent the disease from spreading."

Livestock officials yesterday intercepted a truck loaded with 700 hatching ducks bound for Nakhon Pathom. The transport of fowl from bird-flu outbreak zones is an offence.

Public Health Ministry's spokesman Dr Suphan Srithamma said three Angthong residents were now put on close medical surveillance because they had running nose and lived in an area where the fowls recently died suspiciously.

"So far, they don't have fever and initial tests don't detect the bird-flu virus," Suphan said.

He also dismissed speculations that 30 students at a school in Angthong's Sawaengha district caught the bird flu.

"Lab tests confirm that none of them caught the bird flu," Suphan said.

In addition to Angthong, two other infected provinces are Nong Khai and Phitsanulok.

In Phitsanulok, lab tests conducted last month confirm fowl in Muang district had contracted the flu. There have now been suspicious fowl deaths in Noen Maprang district, where earlier testing was negative.

"We collected more specimens for testing on February 1 and are waiting for the results," Noen Maprang livestock authority chief Anon Chulapakdeekuanoon said.

On Thursday, 82 chickens at a Noen Maprang village were culled following fowl deaths.

Noen Maprang district chief Kriangwich Kairopwimon met with kamnan and village heads yesterday.

Disinfectant spray has been distributed to each village.

Interior Minister Aree Wongsearaya said prevention was the top priority for officials.

"We have instructed provincial governors, district chiefs and local administrative organisations to work closely with other authorities," he said.

In a related development, Public Health Minister Mongkol na Songkhla said World Health Organisation director-general Dr Margaret Chan had praised Thailand for its clear and coordinated bird-flu control measures.