Fears of another significant pollution incident in the River Crane have emerged after reports of a green tinge in the water.

The Friends of River Crane Environment (Force) is concerned about the wildlife in the river after an apparent incident in the lower Crane.

In early March the group received several reports from people that caused concern, including a photograph of polluted water coming from the Heathrow outfall, along with small dead fish.

A couple of days later a Force member, taking children river-dipping at Crane Park, recorded the river bed as being covered in filamentous growth and that the invertebrate life of the river had been badly affected.

Later in the week he inspected the river above and below the Heathrow Outfall and found a thick slime layer below, with low numbers of invertebrates.

Above the outfall the water and river bed were clear and there was a much wider selection of river life.

The incident has been reported to the Environment Agency and the Crane Valley Partnership.

Rob Gray, chairman of Force, said: “Force has been working with Crane Valley Partnership and others to monitor the river’s recovery and put in place measures to increase its value and reduce its vulnerability to regular pollution incidents.

“These latest developments are therefore of great concern to us."

Late last year the Environment Agency began a fish restocking programme in the river, which was recovering from a pollution spill in November 2011.