KUALA LUMPUR, Sept 27 — Air quality in Petaling Jaya, Port Klang, Shah Alam and Batu Muda, areas surrounding Kuala Lumpur in Malaysia, worsened to “very unhealthy” levels as a gauge in Singapore remained in the “moderate” range.

The Air Pollutant Index was between 226 and 279 in the four Kuala Lumpur districts as of 10am local time, according to data posted on the Malaysian Department of Environment website. Singapore reported Sunday that its three-hour pollutant standards index stood at 74 at 10am.

Smoke from Indonesian forest fires has blanketed the region with a layer of haze in the past few weeks. The measure in Singapore had climbed to one-year high of 334 on Friday morning, a reading classified as “hazardous”, prompting the shutting of schools and suspension of some outdoor events. The city state named four Indonesian companies it believes may have contributed to the smoke and said it would apply more pressure on palm-oil and forestry businesses responsible for the blazes.

Investigations aided by meteorological data and satellite imagery showed fires on Indonesian land concessions controlled by PT Rimba Hutani Mas, PT Sebangun Bumi Andalas Wood Industries, PT Bumi Sriwijaya Sentosa and PT Wachyuni Mandira, the environment & water resources ministry said in a statement. Representatives of the companies couldn’t be reached for comment by telephone yesterday.

The ministry also said it served Singapore-based Asia Pulp & Paper Co with a notice for information on its subsidiaries, as well as measures taken by its suppliers in Indonesia to put out fires in their concessions. Aniela Maria, listed as the media contact person on the company’s website, didn’t immediately reply to an e-mail seeking comment today. — Bloomberg