At least 900 of 1,300 small enterprises in Malang regency, East Java, dump their untreated waste into the rivers, an official says.

During the rainy season, pollution was apparent as the water was heavily contaminated with waste, head of the Environment Agency in the regency Cholis Bidajati was quoted by antaranews.com as saying on Monday.

He said that most of the delinquent companies did not possess environment impact analysis documents as well as other necessary papers regarding waste management.

He urged the companies to undertake an environment impact analysis and threatened to take administrative action against those that failed to do so.