The move follows the mass culling of 300,000 chickens at 78 farms in Nakhon Phanom province on the weekend.

The Public Health Ministry is closely monitoring 765 people who took part in the slaughtering, fearing they might have been exposed to the potentially deadly bird-flu virus.

Caretaker Public Health Minister Pinij Charusombat said all 633 people involved in the culling, plus 111 farm workers, 18 people in the families that operated the farms and three other villagers were put on the provincial bird-flu watch list.

The minister was speaking during a trip to Na Klang district in the north-eastern province where the H5N1 virus was detected.

All 765 people on the list would be monitored for 14 days.

So far, six people had developed a high fever, Pinij said. Two of them had influenza symptoms and had received oseltamivir, the only anti-viral drug that can be used to treat people infected with H5N1. The other four had tested negative for the influenza virus.

He said surveillance and disinfecting in the province had to be stepped up.

The Medical Science Department yesterday sent a mobile laboratory unit to the Nakhon Phanom provincial hospital to conduct further tests on suspected cases.

Pinij ordered the province's public health office to set up a bird-flu advisory team to assist and give advice to community hospitals on how to detect the H5N1 virus in humans and on the appropriate use of oseltamivir.

Besides Nakhon Phanom's Naklang sub-district, there were 45 suspected cases of human infection in 10 provinces, said Pratch Boonyawongwiroj, permanent secretary of the Public Health Ministry.

Fifteen cases were in Sukhothai, eight in Phitsanulok, seven in Suphan Buri, six in Phrae, three in other districts of Nakhon Phanom, and two in Phetchabun. Nakhon Nayok, Uttaradit and Phichit reported one case each.

Pratch said there were no other confirmed cases in Phichit besides that of a 17-year-old boy who died late last month.

Meanwhile, the Department of Livestock Development (DLD) yesterday blamed a "neighbouring country" as the source of the bird-flu outbreak in Nakhon Phanom.

Yukol Limlamthong, the DLD's director general, said his inquiries had found the H5N1 virus entered chicken farms in Nakhon Phanom via egg trays farm workers took from their customers on "the other side" [of the Mekong River].

The province is located on the bank of the Mekong River which forms a natural border between Thailand and Laos. The Lao government last week admitted that much of its poultry population had been infected with the bird-flu virus.

Sudarat yesterday banned the import of all chicken-farm accessories (including egg trays) from neighbouring countries. She said the outbreak in the province had been contained.

Yukol insisted the H5N1 virus had only been detected in Phichit's Bang Moon Nak district and Nakhon Phanom's Na Klang sub-district, despite reports of chickens dying of suspicious causes in other provinces. The first human bird-flu victim this year died in Phichit's Tap Klo district.

"I am also wondering why there are confirmed human cases in areas where the virus is not found in poultry. Medical doctors have to investigate," he said in a telephone interview.

Under the Agriculture Ministry's latest epidemic control measures, anyone found transporting birds illegally, dumping poultry carcasses in natural waterways or burying dead poultry without informing livestock officials would face a fine or jail.