The authorities in Ghana are trying to find out what has caused more than 60 dead dolphins to wash up on several beaches.
Local fishermen say the phenomenon is extremely rare.
Officials are warning against eating the dolphins and various other fish species that have also washed up, as it not yet clear what caused their deaths.
Ghana's Fisheries Commission says samples have been taken for laboratory analysis.
Dozens of dolphins went missing from Axim beach in the west of the country. It is suspected they were taken away by people who intend to sell their meat, Ghanaian news site Graphic Online reports.
"Initial observation... showed no wound/lesions on their bodies... The colour of the sea and temperature are normal," the executive director of the Fisheries Commission, Michael Arthur-Dadzie, is quoted by AFP news agency as saying.
Investigations have taken place over the last year after similar mass dolphin deaths along other parts of the African coast.
In February 111 dolphins were found dead off the coast of Mozambique.
The dolphins may have got caught at low tide after Cyclone Guambe, a preliminary investigation by Mozambique's agriculture ministry suggests.
Last year, 52 dead dolphins were found on the coast of the Indian Ocean island of Mauritius.
An investigation by Mauritius's fisheries ministry put the main cause of death down to a phenomenon known as barotrauma.
This results from an abrupt change in pressure which can be caused by various things including military sonar, an underwater earthquake, explosives or a volcanic eruption.
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