Singapore – Mild haze in Singapore and Malaysia could rapidly get worse, with more smoke blowing in from forest fires on the Indonesian island of Sumatra, officials said Wednesday.

In Malaysia, a gray pall hung over Kuala Lumpur, obscuring the upper floors of the city's skyscrapers and the Petronas Twin Towers, the world's tallest building.

Meteorologists at the Kuala Lumpur airport confirmed the haze, but said it wasn't serious enough to start affecting flights. Malaysia's meteorological department declined to give air pollution figures or even confirm that there was a haze.

In Singapore, just south of Malaysia, officials admitted there was a potential problem. "We might get some slight haze over the next couple of days," said Wong Teo Suan, deputy director of Singapore's Meteorological Service Department.

The city-state's Pollutant Standards Index shot up from a safe 30 early Wednesday to a worrying level within hours. At 11am, the Index had crept up to 51. A reading of 50 or below is considered "good," while higher than 50 is "moderate" and higher than 100 "unhealthy." Indonesian fires, often set deliberately by logging and plantation companies as an inexpensive, but illegal way of clearing land, have become an annual problem during the dry season in Southeast Asia.

The situation was particularly severe in 1997 during the dry El Nino climate phenomenon, when thick smoke spread to Singapore and parts of Malaysia, causing respiratory problems for people and even affecting flights.

Earlier this week, Singapore's environment ministry said it had detected more than 90 hot spots in central Sumatra. Hot spots are areas where the temperature is abnormally high, generally indicating a fire.

Officials warned that haze could blanket Singapore and Malaysia if the fires continued to spread, and if the dry weather holds.

Satellite pictures released by the environment ministry showed smoke drifting from Sumatra toward peninsular Malaysia, which lies west of the Indonesian island, just across the narrow Malacca Straits. "By yesterday, some of that smoke would have reached the west coast of peninsular Malaysia," Wong said Wednesday.

Singapore has been spared from the worst effect of the Sumatran smoke so far, but if the fires spread, conditions could deteriorate, Wong said.