Thousands of diesel oil have leaked into the River Lune, the Environment Agency revealed yesterday. Thieves were trying to steal fuel from a storage tank at a lorry depot in Heysham, Lancs.

After efforts to siphon the tank failed they removed a valve, causing more than 8000 gallons to gush out. The raiders fled, leaving fuel leaking into the river.

A spokesperson from the Environment Agency said it was a “major incident.”

“We are very concerned about the environmental impact and are expecting to see a lot of dead fish and birds,” she said.

“This is a conservation area, particularly for water birds, and we are currently working very hard to contain the spillage using inflatable barriers.”

Police are appealing for witnesses as experts prepared to work through the night to minimise damage.

EA officials later said the spillage had been contained and only a small quantity of oil had reached the estuary.

“It’s affected about a mile of the watercourse and tributaries on the Lune,” a spokesman said.

“Only a small proportion of the diesel spill has reached the estuary as it’s being sucked off the surface of the water into special vacuum tankers.”

Some dead fish had been seen, she added, but no other casualties reported.