( CNN ) -- Environmental authorities are investigating the deaths of more than 800 dolphins that have washed up on the northern coast of Peru this year . The dolphins may have died from an outbreak of Morbillivirus or Brucella bacteria , said Peruvian Deputy Environment Minister Gabriel Quijandria , according to Peru 's state-run Andina news agency . Speaking to CNN , he said he expects test results to be ready within the week . `` Right now , the most probable hypothesis is that it 's a virus outbreak , '' he said . Quijandria said Thursday that 877 dolphins have washed up in a 220-kilometer ( 137-mile ) area from Punta Aguja to Lambayeque , in the north of the country . More than 80 % of those dolphins were found in an advanced state of decomposition , making it difficult to study their deaths , according to Andina . Earlier last week , the Peruvian government put together a panel from different ministries to analyze a report by the Peruvian Sea Institute ( IMARPE ) . Officials have been able to conclude that the dolphins ' deaths were not due to lack of food , interaction with fisheries , poisoning with pesticides , biotoxin poisoning or contamination by heavy metals . `` When you have something this large , my gut would tell me that there 's something traumatic that happened , '' Sue Rocca , a marine biologist with the Whale and Dolphin Conservation Society , told CNN . She floated a number of number of possibilities as to what could have killed the animals , including acoustic trauma , but concluded that investigators just do n't know yet . `` More investigation needs to be done , '' she said . The dolphin deaths in Peru are mark the third set of high-profile strandings in about two months . In February , 179 dolphins -- 108 of which were dead -- washed ashore in Cape Cod , in eastern United States , according to the International Fund for Animal Welfare . Marine biologists are still trying to determine the cause of those deaths . In early March , amateur video taken from a beach in Rio de Janeiro , Brazil , showed more than 30 dolphins on shore . In that instance , all dolphins were safely returned to the sea .
NEW : `` More investigation needs to be done , '' says a marine biologist . Official : The dolphins were found over a 220-kilometer ( 137-mile ) area of coastal the United States early March . The dolphins were not caused by starvation or poisoning with pesticides , officials say . more than 800 of dolphins have also washed up in Brazil and the United States this year .