The Environment Agency is appealing for information after a serious pollution incident led to the death of almost 3,000 fish in Scarborough.
It received a report on Sunday August 5 that a number of dead fish had been spotted in the Burniston Beck, between Cloughton and Scalby.
Officers believe it was caused deliberately and have vowed to prosecute those responsible.
An officer visited the beck the same day and found around 60 dead fish, including trout and bullheads, within a 100m stretch at Rocks Lane, Burniston.
Further inspection revealed hundreds more dead fish between Burniston Community Centre and Station Road in Scalby.
Other officers were called to the area and samples were taken in an attempt to locate how and where the pollution started.
Since the initial report the agency has taken numerous calls about the incident, some of which suggest it may have occurred on Saturday August 4.
The incident was confined to Burniston Beck, and although the estimated number of dead fish is just less than 3,000, including over 800 brown trout, live fish have since been seen swimming in the beck.
The survey also showed that the local invertebrates appear to be unaffected. A survey to determine the number of fish remaining in the beck will be carried out shortly.