In Bratislava, Slovakia, around 17,000 litres of what is believed to be crude oil has leaked into the Danube River and the Little Danube.
The incident occurred at the Winter Port’s Mále Pálenisko transshipment terminal.
An anchored tugboat was holding the substance, which is believed to have escaped from a faulty pumping tube.
A worker at the terminal noticed the problem early on 12 June as he transferred oil into a vessel, and called emergency services. Nineteen fire engines and 39 fire fighters were called to the scene.
A criminal investigation has been launched into water and air violations.