Fish died and an angling competition was called off after chlorine spilled into the River Thames.

The murky green water at Abingdon suddenly turned blue and hundreds of dead fish floated to the surface.

The pollution drifted downstream from Abingdon and affected half-a-mile of water along the Culham Reach towards Sutton Courtenay.

An investigation launched by the Environment Agency into Friday's incident was continuing today. It was the second case of river pollution in Oxfordshire. Last week, hundreds of dead fish were found in the River Cherwell at Banbury.

The incident at Abingdon led to the annual children's fishing competition, organised by Abingdon Town Council, being abandoned at the last minute. It is expected to be rearranged in September.

Jim Richardson, licensee of The Old Anchor pub on St Helen's Wharf, overlooking the river, was one of the first to raise the alarm.

He said: "It was horrendous it just killed everything.

The water went a pale bluey-green colour, almost as if it was the Mediterranean, and some people were coming in saying how nice it looked. But you could smell the chemical, it was just like bleach.

"Two-thirds of the river's width outside here was affected and the dead fish were coming up everywhere."

A spokesman for the Environment Agency, whose environmental protection officers spent Saturday gathering water samples for analysis at their Reading laboratories, said: "We're still gathering evidence which could possibly lead to a prosecution." Agency officials are working with environmental health officers from the Vale of White Horse district council to trace the source of the pollution.