BELGRADE (Reuters) - Serbian police and the state security agency have uncovered a massive stockpile of toxic waste and arrested the owner of the company that illegally stored it, the government said on Friday.

The 25 tonnes of waste, in poorly sealed barrels containing various chemicals including benzene and toluene, was found in a privately-owned storage area in the Obrenovac municipality, around 50 kilometres southwest of Belgrade.

The police action and an ongoing clean-up effort averted “an environmental catastrophe”, Goran Trivan, Serbia’s Environment Minister, told reporters.

Trivan said investigators were trying to ascertain whether chemicals had seeped into the soil and contaminated wells.

“No one will remain unpunished ... for failing to treat dangerous waste in line with the law and for endangering the health of the people,” he said.

In a separate statement, the Interior Ministry said that the owner of the company which operated the storage had been detained and charged with endangering public safety.

Serbia, which wants to join the European Union, is heavily polluted due to decades of mismanagement and the operation of obsolete industrial facilities.

As part of the EU membership process, Belgrade must complete talks which cover the environment and climate change.

The successful completion of these talks would come with a hefty bill of at least 10 billion euros ($17.99 billion) which must be invested in environmental protection including waste storage and sewage treatment.

Serbia’s government will have to find around 8 billion euros, or 8 percent of its gross domestic product, to comply while the remainder would be made available from EU funds if it joined in 2025, as planned.

($1 = 0.8338 euros)