Water quality in the River Nene at Peterborough has now almost returned to normal with no more fish dying as a result of the chemical pollution.
People are advised to take the usual precautions when being in contact with river water such as covering up cuts and not swallowing the water.
A ban on fishing for shellfish in The Wash following a pollution scare is set to be lifted after tests by the Food Standards Agency.
The fishing fleet at King's Lynn has been laid up for two days after 5,000 litres of pesticide spilled into the River Nene near Peterborough and there were fears it had flowed out to sea.
Water samples taken from the River Nene in Peterborough by the Environment Agency have confirmed that the immediate danger to fish from a chemical spill has passed.
Officials say chemical levels are now low and they expect the river to return to normal over the next few days.
Wednesday was a frustrating day in port for the crews of 30 fishing boats at King's Lynn in Norfolk after they were banned from catching shellfish after a chemical spill.
Thousands of fish were killed after 5,000 litres of pesticides spilled into the River Nene near Peterborough. It's feared fishing grounds in The Wash may now be contaminated where the river flows into the sea.
The Food Standards Agency has halted fishing while it carries out tests and that ban has been extended into Thursday. The fishermen say they're worried about their livelihoods at what should be their busiest time of the year.