Experts have been working through the night to try to stop toxic water flooding out of a disused mine near Truro.
Pumps are at full capacity at Wheal Jane, but levels there are still rising following heavy rain. It could mean polluted water leaks into the nearby river and Fal Estuary, a marine special area of conservation. The fire brigade has also been called in to help.
In 1992 flooding from the mine turned the estuary into a polluted swamp.
More top news
Jeremy Corbyn's visit has been one of the big talking points of another busy day at Glastonbury.
The Labour leader said socialist politics would not be put "back in a box" as he appeared on stage at the festival.
Turning windier with a few showers