Air pollution in Dumai, the epicentre of last year's extreme haze, soared to very hazardous levels on Tuesday morning, as the dry season - and open burning - started much earlier this year.
The Air Pollutant Index in Dumai, Riau province, surged on Tuesday to 449, close to levels seen at the peak of the haze last June, when Indonesia was forced to dump water from airplanes to douse forest fires.
Dumai, some 270km northwest of Singapore, was at the centre of the worst haze in years last year as farmers slashed and burned to clear land, causing air pollution to hit record highs in nearby Singapore and Malaysia.
On Tuesday, the number of hot spots in Sumatra more than doubled to over 450, from about 190 a day earlier, according to the National Oceanic and Atmospheric Administration satellite.
For now, winds are blowing away from Singapore and Peninsular Malaysia, said Agus Wibowo, head of the data department at Indonesia's disaster mitigation agency (BNPB). He said there were no reports of the two neighbouring countries being affected by haze so far.
In Siak district, south-east of Dumai, 210 schools were closed and students sent home on Tuesday. Schools are expected to remain closed at least until Wednesday, after fire raged in a sago plantation owned by PT Nasional Sago Prima in a neighbouring district of Meranti Islands.
Flights in Pekanbaru, Riau and Palembang, South Sumatra, were delayed this week due to low visibility.
Farmers and plantation companies in Sumatra and Kalimantan, faced with unusually dry weather over the past few weeks, have been burning to clear land, the cheapest way to do so.
Open burning is against the law but the rule is widely flouted.
Provincial heads of the disaster mitigation agency from eight haze-affected provinces, including Riau, North Sumatra and West Kalimantan, called on the government on Tuesday to begin water bombing.
"Most of the fires were caused by deliberate burning by residents, not fire accidents," said BNPB head Syamsul Maarif in an interview, citing reports from the disaster agency's provincial heads. "Many of the fires were near the main roads, access roads, indicating the starting of the fires was deliberate."
The BNPB will help with water bombing and cloud seeding operations by deploying air force aircraft and hired helicopters, said Syamsul.
The agency is gearing up for an especially hot and dry season starting from April, he added.
"Learning from last year's experience, we don't want to be late this time round," he told The Straits Times.
Syamsul said the agency will rent Russian Kamov helicopters with belly tanks that can carry 8,000 litres of water, compared with the 500 litres helicopters in Indonesia can carry. The agency also plans to rent helicopters from Australia, he added.
Meanwhile in Malaysia, Johor's fire department told The Star newspaper that it recorded 1,226 cases of open burning in the southern state between January 1 and February 8, including bushfires, forest fires, fires in plantations and burning of garbage.
That compared with only 1,856 open-burning cases for the whole of last year.
Penang, too, has seen bushfires in the past few weeks due to the dry weather.
In Australia, climate models indicate an increased chance of an El Nino weather pattern emerging later this year, the country's weather bureau said on Tuesday.
El Nino can cause flooding and heavy rains in the United States and South America and trigger drought conditions in Southeast Asia and Australia.