Cyanide ruled out as cause of mass deaths of crab and lobsters washed up on Teesside and North Yorkshire coast

An investigation is continuing with other agencies, including North Eastern Inshore Fisheries and Conservation Authority, into the incident which has seen wash ups as far as Hayburn Wyke to the south of Robin Hoods Bay.

A rumour had been circulating among fishermen that the cause of the deaths was cyanide, dumped at sea in Tees Bay from an industrial site.

However when asked the EA said the deadly chemical was an unlikely cause because only crabs and lobsters have been affected. They said they were keeping an open mind as to the cause.

A spokesperson added: "We would expect to see other marine life, including fish, affected if cyanide was causing these mortalities. The duration and spatial extent of the incident also make this unlikely.”

The agency said last week it had screened for more than 1,000 potential chemical contaminants, but found no anomalies that could lead to such a large-scale event.

The Food Standards Agency says there is no evidence that eating shellfish caught off the coast poses a risk to human health.