A CHEMICAL spill which affected the River Colne near Halstead led to the rescue of more than 8,000 fish.
Around 5,000 litres of pesticide where spilled directly into Toppesfield Brook when a farm trailer overturned on June 13.
The incident saw a 12km (7.4 mile) stretch of the river between Great Yeldham and Earls Colne badly polluted and thousands of fish were killed, despite the efforts of the Environment Agency to minimise the damage.
Following a clean-up operation, the pollution levels in the water now appear to be subsiding, say officials.
Frank Saunders, from the Environment Agency, said: “We are still monitoring the river and pesticide levels, which, are now greatly diluted, so we are not seeing further impact on fish.
“We will continue to carry out sediment and water sampling until we are satisfied that the river has returned to normal.”
It is likely that the river will take some time to recover from the pollution. Officers from the Environment Agency and volunteers from Essex Wildlife Trust spent several days removing dead fish from the affected stretch, while many insects also died.
“This is a major food source for fish and the results of tests will inform us when we can start returning the fish we have rescued back to the river,” said Mr Saunders.
A full investigation into the cause of the spill has been launched.