Russian airlines Vladivostok Avia said it was not guilty in the death of 12 out of 20 fur seals during a flight to a dolphinarium in Russia\'s Far Eastern city of Vladivostok, the company\'s press service said on Friday. Transportation prosecutors began a probe into the death of 12 fur seals on board a Vladivostok-bound plane. The animals died during transit on Monday. According to the preliminary information, the seals, which were being transported from Sakhalin Island, were affected by high temperatures in the plane\'s cargo bay. \"The air carrier officially announces that the actual cause of the fur seals\' deaths remains to be substantiated,\" the carrier said in a statement. The temperature in the cargo bay was about 15-20 degrees Celsius (59-68 degrees Fahrenheit). In line with these circumstances it is too early to make a conclusion about the cause of the seals\' death, the carrier said. Veterinarians have ruled out any diseases the seals may have had. An expert from the Oceanological Institute however said the seals could have suffocated each other as the cargo bay was too small for the 20 adult mammals. Aerogruz, the company responsible for carrying the animals, cited stress as the main reason for the seals\' deaths.