Just a couple of weeks ago, a dead bottlenose dolphin washed ashore at Kuakata's sea beach in Patuakhali.
In the next few days, the number kept increasing, up to five, to the astonishment of the local people who had never seen so many dead dolphins.
The cause of death for those mammals was not immediately determined.
Experts assumed that a recent change in the water quality of the Bay of Bengal might have caused their deaths, according to the Patuakhali administration.
However, some local fishermen said the dolphins might have been caught in the fishing nets in the deep sea which caused their death. Later, fishing boats might have dumped them into the sea and they drifted onto the shore along the sea waves.
The first dead dolphin reached the beach in the second week of July and, later, the number continued to increase.
The dolphins are now lying scattered within two kilometres from the zero point of the beach.
Md Barek Molla, mayor of Kuakata municipality, said the dolphins will be buried on the mainland after the local administration permits them, adding that he had never seen so many dead dolphins in his life.
Molla Imadullah, deputy director of Patuakhali fisheries office, said they have already visited the spot but could not determine the reason for the dolphins' deaths.
Amirul Islam, the principal scientific officer of Bangladesh Fisheries Research Institute, Khepupara in Patuakhali, said they took some samples of seawater and found, on Wednesday, an absence of a proper level of salinity in them.
The Patuakhali administration said they are going to form a probe committee comprising experts in this regard.
"Steps will be taken after getting the investigation report," said Matiul Islam Chawdhury, deputy commissioner of Patuakhali, adding that the committee will start working on it very soon.