In Italy almost half a million litres of fuel fouled the countrys longest river, the Po, on 25 February after pouring into a tributary from storage tanks in what could have been a deliberate act of pollution.
The Lombardy and Emilia Romagna regions in northern Italy asked Rome to declare a state of emergency to help deal with the spill in the Po and its Lambro tributary in the country's richest industrial and agricultural area.
Swift currents have hampered efforts to contain the fuel, mostly diesel.
We are talking about 400,000 litres, Ferruccio Melloni, head of Emilia Romagna's civil protection agency, says.
The fuel poured into the Lambro late on Tuesday from storage tanks at a disused Lombarda Petroli refinery near Monza, about 20 miles northeast of Milan.
Enel SpA, Italy's largest power company, said the fuel formed a layer between 10 and 15 cm thick at its Isola Serafini hydroelectric power plant on the Po.