The central parts of the city and its outskirts were enveloped in a dense shroud of haze caused by two wildfires from the outskirts.
Miri Fire and Rescue Department chief Supt Law Poh Kiong said Bomba Miri were dealing with the two hotspots.
One is in the Tukau area (about 20km south of the city) and the other is in Vista Perdana area (15km north of the city).
"The wildfires were caused by illegal farmers," he said.
The Star last night found visibility reduced to just about 200m in several residential and commercial areas, especially in the Pujut to Lutong stretch.
The air had a thick smell of ashes and caused breathing difficulties for thousands of residents.
In the past two weeks, therehad been a lull in these wildfires following some rain.
However, it looks like the relief will be shortlived. The wildfires in Sarawak had started in early March.