Dog owners are being warned over the dangers of palm oil after the toxic substance was discovered on a west Cumbrian beach.

A tourist found a large boulder-like chunk of palm oil while out with her dog at St Bees.

After suspecting it was the dangerous substance, the woman took it to Hartley's Beach Shop to see if they knew what it was.

Staff confirmed it was palm oil, which can be toxic to dogs.

They have now displayed a sign in the shop window, warning dog owners to be vigilant.

Deborah Hewitson, general assistant at the shop, said: "We'd had a really windy weekend and a lady came in with a big lump of it in her hand.

"She asked me if it was palm oil. I've seen it before over the last few years, so I knew straightaway it was palm oil. It was quite a big piece.

"We chose to put a sign in our window warning dog owners because it's very toxic to dogs.

"A lot of people think it's a liquid that washes up, but it's not. It's a solid. It just looks like a big piece of lard but it's hard.

"If we were to pick it up and put it in the bin, it wouldn't harm us, but if a dog were to eat it, it would be dangerous."

Jenna Lamb, a vet at Millcroft Veterinary Practice, has warned of the symptoms to look out for if a dog may have ingested palm oil.

She said: "The main concern is the dog absorbs the oil from it.

"The most common signs after ingesting it are vomiting and diarrhoea which is usually self-limiting but can cause dehydration.

"In severe cases, if the dog has eaten more, they can get pancreatitis, which can require hospitalisation.

"If they eat a large chunk whole, there's potential for it to cause a blockage in the intestines.

"Occasionally it can bind with things like oil or diesel from ships which can make the upset worse."

She has also advised owners to avoid areas known to have palm oil, and to seek veterinary advice if their dog does come into contact with the substance.

"We advise dog walkers to avoid places where they know it to be and keep their dogs on a lead.

"If they do suspect their dog has eaten palm oil, not to worry, it is self-limiting, but they're best to give us a call to give the dog a check over and proceed with any medications."

Palm oil is an edible vegetable oil derived from palms and used in processed foods, toiletries and as a biofuel.

The substance, often found in boulder-size chunks, is not dangerous to humans but is toxic to dogs.

Ships use it as a tank cleaning agent, meaning it can get in the sea and has been found on beaches along the Cumbrian coast on numerous occasions.