An oil drum dumped in a lane in West Sussex was left to spew its contents along the side of the road, a council has revealed.
The 45 gallon tank was abandoned in Norway Lane, off the A259 in Littlehampton, earlier this week.
Contractors from Arun District Council covered the oil slick with grit, and said it was the worst case of fly-tipping they had seen.
Councillor Paul Wotherspoon described it as "truly appalling".
"Whoever dumped this had no regard whatsoever for the environment or the safety of the public," he added.
The council said if caught, the culprits faced a fine of up to £50,000 or up to five years in prison.