An investigation is underway into a pollution incident which killed around 1,000 fish in a south Wales river.
The river was polluted in the same place last year
Environment Agency Wales was alerted after a member of the public saw a number of dead fish in the River Ebbw at Crumlin, near Newbridge.
Agency officers have been taking samples of the water to try to assess the severity of the pollution.
The river was polluted in the same place in October last year, killing over 4,500 fish.
The agency began its inquiries at around 1430 BST on Sunday after finding around 1,000 dead brown trout and bullhead fish in the river.
They returned to the site on Monday and have since sent river water and fish samples away for analysis.
Two industrial sites, each with a large number of units, have drainage systems which are linked to the river.
Companies based on the Croespenmaen and Pen y Fan industrial estates are being asked to check their drainage systems for blockages or anything else that may have caused the pollution.
They are being advised to contact the agency for advice if a problem is found.
Dai Walters from the agency, said: "We are grateful for the call alerting us to this incident.
The quicker we can respond to an incident, the greater the chances of finding out the source of pollution, and possibly lessening the effect."
On Wednesday a pollution incident on a tributary of the River Loughor in Carmarthenshire killed more than 100 fish.
During the unrelated incident, trout and eels were among those killed after the stream was polluted for almost 500 metres near Ammanford.
Investigations are continuing but it is thought a local source is to blame for the sewage-related pollutant.