Clinics on the outskirts of Kuala Lumpur have received an increase in respiratory complaints in the last 24 hours.
Half the country is affected by the smog, with motorists on the main north-south highway running along the west coast being warned to keep their distance from one another.
Clinics on the outskirts of Kuala Lumpur have received an increase in respiratory complaints in the last 24 hours.
In some areas of the capital, visibility has dropped to one kilometre (0.6 mile), the worst since the 1997-8 crisis, which was triggered by Indonesian forest fires.
Singapore has also been affected by haze in recent weeks.
Visibility in some parts of the straits of Malacca - the world's busiest shipping route, between Malaysia and the Indonesian island of Sumatra, is expected to drop to two kilometres.
One anonymous official told a local newspaper there was no cause for alarm because the situation was only temporary.
Kept in the dark
But newspapers have been bombarded by angry telephone calls from the public, complaining that information is simply not available.
But an opposition party has called for the figures to be released.
"In this era of information technology, it is sheer folly for the government to pretend that it could mislead foreign tourists into believing that there is pure and clean air in the country," said Lim Kit Siang, chairman of the Democratic Action Party.
"Give priority to the health of Malaysians, particulary of the young generation, rather than to the tourism industry," he added.
Slash and burn
Satellite tracking from Singapore shows the current haze is being blown towards Malaysia from Sumatra, where there are thought to be at least a hundred hotspots, areas of forest fires.
In the past, Indonesian plantation companies have been accused of deliberately starting fires to clear the forest for planting.
The haze three years ago was an environmental disaster that is thought to have cost the region $4bn.
It forced children and the elderly to stay indoors and disrupted travel throughout the region.