Investigations into the cause of pollution at Doe Park Reservoir in Denholme , which caused the deaths of 2,500 fish, have revealed the potential source of the contaminant.

Environment Agency staff have been investigating the fish killed at the 20- acre reservoir and have tested both water and fish samples.

Bosses at the agency confirmed they believe they have found a source of the pollution. As the investigation is continuing, they declined to say anything more at the moment.

A team was called to the reservoir on Monday after reports of dead and distressed fish at the site. They found dead roach, bream, perch and pike.

Following an initial examination, fisheries officers said they believed the cause of the pollution was down to organic matter that had been washed into the water through recent flooding.

Ten barrels of hydrogen peroxide were pumped into the reservoir on Monday to help break down organic matter which can cause poor water quality. At the time oxygen levels in the water were found to be good.

Louis Harvey, environment management team leader, said yesterday: “As part of our investigations into the recent serious pollution incident at Doe Park Reservoir, Denholme, near Bradford, we have now had some support from the local community and believe we have found a source of the pollution that killed about 2,500 fish.

“We are continuing to investigate, and cannot comment further at this stage.”

Bradford Council, which operates a water activities centre at the reservoir, was forced to postpone an open day which had been planned for Tuesday.

A spokesman for the authority told the Telegraph & Argus it was still evaluating the situation and as a result were not due to reopen the site next week. The situation will be looked at again towards the end of next week.

Kayaking and canoeing activities are now taking place on the River Aire and the Leeds-Liverpool Canal and alternative activities are being organised.

The reservoir is a compensation reservoir and is used to top up river levels rather than for drinking water.