The authroities do not know the source of foam-like material which has appeared on the coast in St Paul's Bay on several days.
Parliamentary Secretary Roderick Galdes told Nationalist MP Censu Galea in Parliament that tests were being made to establish what the material was and its source.
It was not known whether the material came from nearby fish-farms or other sources, he said. Samples were being tested in laboratories.
Once the nature of the material and its source were established, the appropriate enforcement action would be taken, Mr Galdes said.
He pointed out that in the past there had been occasions of oil-like contamination which was initially blamed on fish-farms but actually stemmed elsewhere.