A dolphin carcass thought to be the bottlenose attraction Marra may have been cut up by council contractors.
A post-mortem examination will establish if the dolphin is Marra
The remains were found in two sacks by a member of the public at Skinburness beach near Silloth, on Tuesday night.
A police and RSPCA probe has begun and Allerdale Borough Council is investigating claims contractors may have cut up the animal for disposal.
The British Divers Marine Life Rescue (BDMLR) said it should have been informed of the discovery.
London's Zoological Society will now carry out a post-mortem examination in order to establish the cause of death.
Marra, a solitary dolphin, became a tourist attraction when she had to be freed from Maryport harbour in January.
Tony Woodley of the BDMLR said: "The council was not obliged in law to inform us of the discovery, but knows we have an ongoing research project into marine life.
"It is concerning that these remains were left in bits in a bag on a public beach overnight for a member of the public to find them."
Marra was rescued from Maryport harbour in January
A spokesman for the council said: "The council has a duty to remove carcasses from the beach.
"The Allerdale Environmental Partnership, which operates refuse collection on behalf of the council, has procedures to deal with incidents like this when marine life has been washed up.
"We now need to speak to the contractor employees involved and find out what has happened.
"However, I'm sure everyone concerned would wish to apologise for any distress caused by the remains being left on the beach overnight."
Marra became a regular feature in the port, but in October people were warned to stay away from her after she was spotted with several wounds, possibly caused by ropes or boats.