Mining is being carried out in a majority of Goa's mines without the mandatory air pollution clearance, Environment Minister Aleixo Sequeira said on Friday.
Sequeria told the assembly that 85 of the 99 mining operators in the state had asked for consent under the Prevention and Control of Pollution Act (PCPA).
He said that in most cases the permission to mine had expired Feb 28.
In a written reply, Sequeira named Sesa Goa, Salgaonkar Industries, Sociedade Fomento and Chowgule as companies operating without consent from the pollution authorities.
The ministry of environment and forests has asked for environment impact assessment of mining activities in the state.
Goa's Rs.6,000-crore mining industry exports nearly 33 million tonnes of manganese and iron ore to countries like China and Japan.