Environment Agency staff have spent the day dealing with an emergency at a canal in Grantham after hundreds of dead fish were discovered this morning.
It's thought they died through lack of oxygen caused by the hot weather.
Chemicals have now been added to the water to bring the oxygen levels back to normal.
Reuben Page from the Environment Agency says that the oxygen levels in the canal are now back to normal.
The oxygen levels were affected by the recent warm weather, which the Environment Agency says usually only affects still water.
The Environment Agency says oxygen levels in Grantham Canal have now returned to normal after the deaths of hundreds of fish.
They were first called to the waterway yesterday and found oxygen levels at around 20%. Since then they have been pumping chemicals into the water to increase the oxygen concentration.
Test have now showed that the oxygen has returned to its normal level. It is believed the recent hot weather, leading to an increase in weed growth, had caused the drop.