The Pollutant Standards Index (PSI) has climbed to a new high of 371 at 1pm on Thursday.
The reading was worse than Tuesday night when the index hit 321 at 10pm.
The previous record was 266, in 1997.
Air becomes "hazardous" when the PSI breaches 300.
Environment Minister Vivian Balakrishnan, in a press conference on Wednesday night, promised that the ministries and agencies have been prepared for the fall-out. The Ministry of Health, for example, has alerted hospitals here to prepare for a spike in patients with respiratory problems. Responding to questions from the media, Dr Balakrishnan said the Manpower Ministry may issue stop-work order and the Education Ministry would have to decide whether to close schools if the haze situation worsens severely.
The National Environment Agency's chief executive Andrew Tan also led a delegation to Indonesia today to an emergency haze meeting convened by the Indonesian Foreign Ministry.
Prime Minister Lee Hsien Loong met with the relevant ministers this morning and will chair a press conference at 3pm on Thursday to address concerns about the smog.
Meanwhile, the National Trades Union Congress, in a statement on Thursday, once again called on all employers to take immediate and proactive measures to ensure that the health and safety of their workers. "Appropriate protective masks must be issued to workers for outdoor work and if they are unwell, they must have the right to stop work and rest indoors," said the statement.
"While no stop-work order has been issued by the relevant authorities at this point, employers should exercise discretion and flexibility where due and make necessary adjustments to their operations, especially where it involves minimising the risks posed by haze exposure to workers."
"Their health and safety are of utmost priority and management must look after their interests over business always."