Indonesia has agreed to share with Singapore the names of companies suspected of causing forest fires that have led to a deterioration of air quality in the city state.

Indonesia's Minister of Environment and Forestry, Siti Nurbaya Bakar, told Singapore's Minister for the Environment and Water Resources, Vivian Balakrishnan, that the names would be shared once the information had been verified, Singapore's National Environment Agency (NEA) said in a statement.

Haze has engulfed Singapore and Malaysia for several days, pushing the PSI air quality index to unhealthy levels of over 100 in the city state on a 24-hour basis. The three-hour gauge of PSI hit a high of 249 late on Monday night, the NEA said.

Singapore passed a cross-border air pollution law last year that makes those who cause haze both criminally and civilly liable. The law also provides law enforcers with a relatively low threshold to prove that a company outside Singapore has polluted the air.

The haze this week is also clouding the build-up to the city-state's glamour sporting spectacle -- the Formula One night motor race that will be held next weekend.