POLLUTION has hit the River Crane again 17 months after a devastating sewage release killed at least 10,000 fish.

Dead fish and a thick layer of slime have been reported on the river, which runs through Cranford, Feltham and Whitton.

Friends of the River Crane Environment (FORCE), a charity set up to protect the river and its surroundings, said members first noticed a 'green tinge' to the water of the lower Crane early last month.

Reports have intensified this month, with one walker capturing pictures of polluted water and dead fish at an outfall by Heathrow and another finding a thick layer of slime.

FORCE secretary Frances Bennett said a thick grey/brown growth was now visible along the lower stretches of the river, while the water remained clear above the Heathrow outfall.

It remains unclear what caused the damage, which has also affected insect life along the river.

A spokesman for Thames Water, which accepted responsibility for the sewage release in 2011, said: "We are aware of these reports but after a careful check of our sewers we don't believe that this latest pollution has any connection to our network."

Ms Bennett said: "The incident has been reported to the Environment Agency and the Crane Valley Partnership and we are awaiting a clear statement from them as to the causes of the pollution and the response to it."

In October 2011, the river was devastated by a huge amount of raw sewage released by Thames Water to prevent it backing up into Heathrow.

There had been promising signs of recovery before Christmas, with insect life beginning to return to the river, and 5,500 fish were released into the water in December.