THE Environment Agency is continuing investigations after an acid substance polluted a Chorley river, killing 5,000 fish.

Fisheries officers are gathering evidence after the fluid was released from industrial premises on Common Bank Industrial Estate into the River Yarrow, killing every fish within a ten mile stretch.

Officers said they were also investigating the drainage system at the industrial estate to see whether it directed the chemicals into the fresh water rather than water treatment works.

The stretch of river, which had been steadily improving in quality over the last five years, was polluted to such an extent that its ph reading was two -- the highest acidic reading possible is one. Brain Shields, Environment Agency fisheries officer said: "This is pretty bad.

"The water quality was improving steadily over the last few years by us working in partnership with companies in the area and stocks were increasing.

"Now with the breeding season just beginning it has happened at a bad time.

"Businesses are allowed to discharge chemicals into the river within set guidelines and under licence so good water quality is maintained.

"But this was just such a toxic fluid. There are also concerns that the drainage system at the estate has been connected wrongly."