Diesel from the bus which caught fire in on Marlborough High Street on Monday morning has flowed into the River Kennet, raising fears about the effect it will have on wildlife.
Wiltshire Fire & Rescue Service was called at 8.34am and crews from Marlborough and Calne tackled the fire, which started in the engine of a Stagecoach bus outside Lloyd’s Bank.
The High Street reopened at 11.45am but Riverside resident Val Compton realised that diesel from the bus was flowing into the river.
She said: "The fumes from the diesel were overwhelming, and the whole river was covered with a film of oil - even four hours later fuel was still coming out from the drains and into the river."
Envirionmental group Action for the River Kennet said all the drains from the High Street run directly to the River Kennet with no cleaning process in between.
And the diesel caused a rainbow film across the water all the way downstream to beyond Pelham Court.
Charlotte Hitchmough, director of ARK, said the group is now discussing with the Environment Agency whether local volunteers can deploy oil-absorbent booms around drain outfalls to contain spills from the High Street in future.
"Although Wiltshire Fire & Rescue Service cleaned up as much diesel as they could at the scene of the accident, an alarming quantity made it to the watercourse," she said.
"This incident illustrates how vulnerable the river is to spills, pollution and run-off from the road.
"It is too early to tell whether the fuel spill will cause lasting harm, but it is a timely reminder that our road drains lead to the river, and whatever goes down them will end up in the Kennet."
Action for the River Kennet is asking people to report pollution by calling the Environment Agency Incident Line - 0800 807060 - as well as telling ARK where the problem hotspots are by emailing email@example.com