The Environment Agency was called out to the town centre park on Saturday afternoon after anglers reported dead fish floating on the top of the water.

Fisherman Mark Brundel who is a member of the Abington Angling Club, said: "We've been losing a few fish over the past few weeks, but we think about 500 have died now.

"The hot weather's certainly not helping, but we also think some kind of chemical might have got into the water.

"When we got down here on Saturday, the fish were actually on the top of the water, gasping for air and we've had a lot of concerned members of the public calling in too saying they're worried about the fish.

"It's a terrible thing for us, because as anglers, the last thing we want to see is fish dying."

Officers from the Environment Agency who were at the park on Saturday afternoon could not confirm what the cause of the problem was.

But their investigations centered on a drain leading from Wellingborough Road into the lake, which the fishermen believe could be the source of the chemical pollution.

In an attempt to revive the fish, the fire brigade were called to help clean up the water.

Using hoses from a fire engine, they pumped water out of the lake then back into it, hoping to increase the water's oxygen levels.