Indonesian has punished 23 companies for causing forest fires that spread thick, smoky haze around Southeast Asia.

The Forestry Ministry's investigations director, Brotestes Panjaitan, said Tuesday that 33 more companies are under scrutiny and waiting for decisions on possible punishment.

Forestry Minister Siti Nurbaya announced Monday that a total of 56 companies were involved in the land-clearing activities that led to the fires.

She added 23 of them, mostly pulp wood and palm oil plantations operating on Sumatra and Borneo islands, have received punishments ranging from administrative sanctions to revocation of licenses.

Forest fires have been an annual problem in Indonesia since mid-1990s, but this year's was the worst since 1997 when blazes spread across nearly 10 million hectares.