It's been confirmed as paraffin wax by the Humber Coastguard, and is thick and yellow-white in appearance.
The material appeared on beaches in the Bridlington area, between Danes Dyke and Fraisthorpe, between Thursday and Friday and visitors were warned to keep away from it until it had been identified. It covers a stretch of coastline several miles in length.
Humber Coastguard said:
"A yellow-white substance has been washed up on the beaches at Bridlington between South Landing and Barmston.
"The waxy substance, which has been confirmed as paraffin wax is of low risk to health.
"The beaches remain open as normal, but as a precaution beach users are advised not to go near the substance. Dog owners in particular are requested to keep their pets away. Please report any further sightings to Humber Coastguard."
Paraffin wax, which is not toxic, has a variety of industrial uses - including in the manufacture of crayons.