Somsak Phothisat, the department's director-general, said the provinces under threat were Mae Hong Son, Tak, Chiang Mai, Chiang Rai, Lampang, Lamphun, Phayao and Phrae.

He said the warning came after a weather forecast said the region was likely to be hit by more heavy rain over the next few days.

The mudslides in Uttaradit, Nan, Phrae, Lampang and Sukhothai in the early hours of Tuesday followed days of heavy rain. Scores of people were killed and many more are still missing, feared dead.

Somsak yesterday rejected criticism that there was no warning system for landslides.

He said the agency had produced a detailed map of 51 provinces and their villages that are considered to be under threat.

The department chief said Uttaradit was worst hit because rainfall there had reached 330 millimetres a day, the heaviest on record for 38 years. Also, the province is surrounded by mountains with steep cliffs covered in loose earth.

He said the department had tried to educate villagers in high-risk areas about the threat of mudslides and also set up groups of volunteers headed by community leaders to monitor rainfall and issue warnings when it exceeds 100mm a day.

Somsak said training courses had been held for volunteers in Mae Hong Son, Chiang Mai, Chiang Rai, Tak, Phrae and Nan, as well as most southern provinces. Preparations for a course to be held in Uttaradit were being made.