In the province of Riau onSumatra island, local authorities have advised people to stay indoors after visibility was reduced to as little as 100 metres, and drivers have been forced to use their headlights in the middle of the day. Emergency warnings have been issued to drivers, airlines and to shipping in the Straits of Malacca between Sumatra and Malaysia, one of the world's busiest and most strategically important waterways.
In Pekanbaru, the province's capital, measurements on the air pollution index have regularly shown levels of smoke dangerous to health, and lower levels have been recorded in Singapore and Malaysia as the smoke drifts across the straits. According to European scientists in Sumatra, the fires are likely to burn until October and their effects could be as bad as, or worse, than in 1997.
"The situation is very, very similar and the way the fires are developing is similar to 1997," said Ivan Anderson, satellite system manager for a European Union fire prevention project in Sumatra. "It has happened before and there is no reason to expect that it will not happen again."
Between the summer of 1997 and the spring of 1998, 10 million hectares of land were burnt in Sumatra and Borneo with catastrophic consequences. The fires damaged some of the world's richest and most delicate rainforests, and killed or displaced endangered species such as proboscis monkeys and orang-utans. Shipping collisions, traffic accidents and at least one passenger aircraft crash were blamed on the smog, and billions of dollars were lost because of cancelled flights, closed airports and absent tourists.
Schools and offices all over the region were closed, and thousands of people suffered asthma, bronchitis and breathing difficulties. In Sumatra, measurements on the air pollution index have regularly shown levels of pollution damaging to human health. An index reading of more than 100 is regarded as unhealthy, and more than 300 is dangerous. Last week, the reading in Riau reached 978.
The fires are man-made, caused by local people clearing land for subsistence farming but mostly by plantation companies that convert huge areas of forest for rubber and oil palm production. Satellite monitoring reveals as many as 450 "hot spots" indicating individual fires. Yesterday, the Indonesian Environment minister, Panangian Siregar, reported seeing 280 fires during a flight over parts of Borneo.
Once the fires rage out of control there is little that a country as poor as Indonesia can do to put them out. Regulations restricting burning during dry periods are routinely ignored by companies, and local authorities have little power or incentive to track down violators. "Enforcement is very weak," said Togu Manurung, of the World Wide Fund for Nature, Indonesia. "I think the fires will continue at least during the whole dry season."
Last year the smog, or "haze" as it is euphemistically known in South- east Asia, caused muted fury among Indonesia's neighbours. Brunei recently threatened to sue Indonesia for damages incurred by the smog, particularly if it disrupted the South-east Asian Games, which are being held there at the moment.