Experts are investigating the first confirmed stranding of an orca in England and Wales for almost 20 years, the Zoological Society of London has said.

The juvenile male killer whale, approximately 15ft long, became stranded in salt marsh in the Wash on the east coast of England.

It is the first confirmed orca stranding that the Cetacean Strandings Investigation Programme, of which ZSL is a partner, has investigated in England and Wales since 2001.

Orcas are a priority species for research by ZSL as they are top predators that can absorb significant concentrations of marine pollutants, such as chemicals known as PCBs, which accumulate as they go up the food chain.

ZSL’s Rob Deaville and Matt Perkins collected blubber, liver, muscle and kidney samples from the mammal, which was internally mostly intact despite its decomposed condition, having probably died weeks ago.

Tests will analyse the samples for marine contaminants, while genetic analysis will help determine which population the animal came from, and teeth have been collected to accurately assess its age.

The experts said there was no evidence of recent feeding as its stomachs were largely empty. The team found a large fragment of plastic in the first stomach, though they said it had not killed the orca as the stomach was not blocked.