The Environment Agency has confirmed that river life along a seven mile stretch of a tributary of the River Thames has been wiped out following a devastating raw sewage spill.

An estimated 3,000 fish have been killed so far following the major pollution incident spill on the River Crane and the Duke of Northumberlands near Twickenham on Saturday. Environment officers at the scene are continuing to assess the full impact of the incident on other river life. Among the species of fish killed are mature pike, eel and perch.

The Environment Agency has launched a full investigation which could lead to a prosecution, following the incident in West London.

Environment Agency Officers have been working around the clock with Thames Water to try to minimise any further environmental damage, taking water samples, monitoring levels of dissolved oxygen and ammonia in the river. Officers are also working to clear dead fish from the water.

The sewage has now been recorded entering the River Thames, at this stage it has not caused any significant impact. However, Environment Agency Officers are closely monitoring the situation.

Environment Agency Area Manager Julia Simpson said:

“This is the most serious incident we have had on a tributary of the River Thames for several years. We worked around the clock to try and minimise the environmental damage from this incident, but today it is clear that stretch of the tributaries have been devastated. Our officers are out by the river today helping Thames Water with the clearing of dead fish from the river.

"We have launched a full investigation into this devastating pollution which has caused the death of approximately 3000 fish on seven miles of river."

The Agency is still advising people to keep both people and pets out of the water until the incident has been resolved.

Thames Water pledges to repair damage

 Thames Water has pledged to help put right the environmental damage caused by the spill which happened when a sluice gate jammed closed in a major sewer serving Heathrow Airport.

The six-tonne, cast-iron penstock, used for controlling flows, jammed closed on Saturday morning in a trunk sewer at Cranford Bridge on the A4 Bath Road while engineers carried out routine maintenance. Attempts to re-open the sluice gate were not successful until 8am on Monday, when engineers used a custom-made lifting device to force it open.

Although the engineers were able to take a lot of the backed-up sewage away in tanker lorries for treatment, Thames said the volume of sewage was such that they were not able to tanker all of it.

Faced with the choice of letting the remaining sewage back up into the airport or spill to the River Crane, the company said it was forced to opt for the latter. From Saturday until 3am on Monday sewage spilled intermittently to the river.

Martin Baggs, Chief Executive of Thames Water said the company deeply regretted the incident and was committed to put things right over the long term.