Occurred during September to November 1997. It was caused not only by external sources that exacerbated the contribution from internal sources but also coincided with the El Nino, which prolonged the dry season in that year. The air quality worsened at several places in Sarawak to such an extent that between 19 September to 28 September (10 days), a Haze Emergency had to be declared in Sarawak when the Air Pollutant Index (API) reached above the 500 level. The air quality returned to normal in November coinciding with the monsoon season.