MAE HONG SON -- The air quality in this northern province is now at a critical level due to haze and smoke from wildfire, governor Pipat Ekphaphan said on Monday.

The level of dust particles measuring less than 10 micrometres, or PM10, on Monday morning was at 264 microgrammes per cubic metre (ug/cu m), up from yesterday's 238 ug/cu m.

The maximum safe PM10 level is set at 120 ug/cu m.

Many people were suffering eye irritations and respiratory problems because of the haze and smoke.

Provincial natural resources and environment officials flew over Muang district by helicopter on Sunday to examine the fire situation. They reported fires burning at two spots - Moo 1 and Moo 12 villages of tambon Pha Bong.

The helicopter made 40 trips dropping water on the flames. The fires had been brought under control.

From Jan 1 to March 19 authorities had found a total of 393 hotspots - 94 in Mae Sariang, 77 in Sop Moei, 70 in Mae La Noi, 62 in Pai, 45 in Muang, 26 in Khun Yuam and 19 in Pang Ma Pha districts.

Mr Pipat said people should not burn garbage or agricultural waste.  He believed this year's haze was the worst in many years.

Karon Air cancelled six flights between Chiang Mai and Mae Hong Son during the past week because of the poor visibility.