Ninety-eight birds, mostly sea ducks, guillemots and razorbills, were found on the 70-mile stretch between Amble in Northumberland and Roker in Sunderland over the weekend, and more calls are coming in.

Now rescuers have set up a collection point where members of the public can drop them off.

RSPCA chief inspector Michelle Charlton said: "We need anyone who finds a bird to bring it direct to the Blue Reef Aquarium on the seafront at Tynemouth, if they can.

"The stretch of coastline is just so large that it's proving really difficult for us to get out to every call and collect every bird.

"Any help the public can offer is very welcome indeed."

Anyone who does come across a bird should take care to look after their own health and safety, in the first instance.

Gloves should be worn, as the pollutant is still unknown, as well as strong clothing.

Care should also be taken when handling the bird, which it should be remembered, is wild and unaccustomed to human contact, and will likely peck as a result.

All of the birds brought to the collection point will then receive the treatment they need.

Chief inspector Charlton said: "We don't know what the cause is yet, and that is not for the RSPCA to establish.

"Our concern is the welfare of the birds being brought in to us, and we are focussing all of our attention on that."

Anyone who finds a bird and can't get it to the collection point should call the RSPCA 24-hour cruelty line on 0300 1234 999.