SINGAPORE — In its fight against the haze that has blanketed the Southeast Asian region, Indonesia has arrested seven executives from companies accused of being behind forest fires in Sumatra and Kalimantan.

The smog is coming from agricultural fires that farmers have created because many in Indonesia still employ the illegal slash-and-burn method of clearing vegetation. Many of the plantations grow pulp for paper and palm corporations.

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The executives were arrested on Indonesia's Sumatra island, says ChannelNewsAsia, quoting national police chief Badrodin Haiti.

The Straits Times is reporting that one of the seven is a senior executive from Indonesia's largest pulp and paper producer, Bumi Mekar Hijau.

The company belongs to Singapore-based Asia Pulp and Paper (APP). Its Indonesia-based media person didn't respond immediately to our request for more information.

This follows reports of over 70 farm owners being detained last week on suspicion of burning their land.

Military personnel try to contain a wildfire on a field in Indralaya, South Sumatra. Image: Tatan Syuflana/Associated Press

Indonesia continues to struggle with fighting against the haze, which has been a perennial issue for the country. In Sumatra and Kalimantan (also known as Borneo), burning crops is a common practice that continues to happen each year despite being outlawed.

Both areas are on separate bodies of land separated by the Java Sea. Two weeks ago, Jakarta deployed 1,000 troops in Sumatra and 1,500 in Kalimantan.

But as the fires rage, air quality has reached alarming states in parts just downwind from the fire. Palangkaraya, in central Kalimantan, reportedly reached 712 on the air quality index on Friday, as measured by the Indonesian Department of Meteorology, Climatology and Geophysics. Anything above 300 is considered "severely polluted."

173 Malaysians to be evacuated from Pekanbaru, Indonesia due to #haze, says the Ministry of Foreign Affairs — Sumisha Naidu (@sumishanaidu) September 18, 2015

Pekanbaru is the capital of Riau in Sumatra.

A worker at the spectator stands for the Singapore Formula One night race during a hazy day. Image: Ng Han Guan/Associated Press

In neighbouring Singapore, the haze has been hovering between the unhealthy range of 101-200 for the past few weeks.

To the north of Singapore, Malaysia's haze has improved since it hit the high 100s last week, and is back down to just below 100 now.

Last week, Malaysia had to close its schools in states like the capital Kuala Lumpur, Selangor and Malacca, affecting about 1.5 million students, reported The New Paper.