Trout were among the fish killed

An insecticide accidentally leaked into the River Slea in February killing thousands of fish.

The incident was uncovered when a passer-by spotted hundreds of dead fish on a stretch of the river near Sleaford town centre.

The Environment Agency says 5,000 roach will be released into the river on Tuesday followed by another 12,000 over the next few months.

Perch and pike

Investigators say the fish kill was caused by the agro-chemical cypermethrin.

The agency says tests show the water quality is good enough to sustain a healthy fish population.

The spill in February spread along a 13-mile (21-kilometre) stretch of the river, devastating fish stocks.

Brown trout, dace, perch, pike, roach, tench and eels were killed when the chemical was released into the surface water drains of an industrial site.

The spill was described as one of the most severe river pollution incidents in Lincolnshire in living memory.