Emergency workers try to contain slick moving down Italy's largest river.
A spill that sent massive amounts of oil into northern Italy's Po River was a deliberate act of vandalism, officials say.
The officials described the spill as a "criminal act" and said someone opened a valve on an oil tank at a former refinery near Milan.
The Po, Italy's longest river, flows more than 640km from the Cottian Alps to the Adriatic and is connected with Milan by a series of canals.