environmental campaigners warned of a pending disaster wednesday as a massive oil slick flowed down italy 's po river after saboteurs broke into a disused refinery and released the spill .
Can you generate a short summary of the above paragraph?

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
user
sabotage puts massive oil slick in italy 's po river