Dog walkers are being urged to be extra vigilant after yellow lumps of suspected palm oil were washed up on the beach at Morecambe.
Palm oil can be attractive to dogs but can kill them if they eat it.
Jessica Ball was in Morecambe on Sunday when she saw the yellowey substance on the beach near the clock tower.
She said: “It could be toxic waste or whale vomit. It was very smelly, very rough and moonrock-like not mushy or oily.”
A spokesman for Lancaster City Council said: “Although we have not received any reports of a substance being washed up on the beach, our cleansing team visited the beach on Monday following high tide to remove what remained of a substance which did look very much like palm oil.
“We will continue to visit the beach throughout the week in the event of more being washed up and would urge local dog walkers to be extra vigilant at this time.”
Wyre Council also said they had received reports of an unknown substance washed up on beaches between Knott End, Fleetwood and Cleveleys on Sunday, November 5.
On their Facebook page, Wyre Borough Council said: “The Environment Agency is aware and we are working closely to monitor the incident.
Tests are being carried out to identify the substance, and partners from the Marine and Coastguard Agency are gathering information on the location and quantity.
“The substance can be described as fatty, oily, greasy with a rancid aroma and bright orange in colour.
“Our rangers are patrolling the beaches to monitor the situation and provide updates regularly.
“So far, substances have been found on beaches in Knott End, Fleetwood and Cleveleys.
“The beaches remain open, but we advise to supervise children carefully and keep your dog on a lead.
“Please avoid all contact with residue on the beach and in the water due to potential health risks.
A spokesman for the Environment Agency said: “The Environment Agency is aware of a substance which has been washed up on the Lancashire and south Cumbria coast line, and are working closely with partners.
“There are numerous suggestions as to the source of the material, however this has not yet been confirmed. “Tests will begin to identify the substance, which are being led by the Local Authorities involved.
“We continue to work with partners to advise and support.”