Five young swans that were living along the Charles River Esplanade are being tested for bird flu after their parents showed symptoms of the infection and were euthanized. An animal control officer and firefighters captured the adult swans on Monday. They were taken to the city's animal care facility, where officials identified "symptoms consistent with avian influenza." The five cygnets were captured Wednesday morning and taken to the Cape Wildlife Center in Barnstable, where officials said the staff will test the birds for avian flu. The siblings will be isolated from other animals until the test results come back, which could take between 48 and 72 hours.Video from a witness shows the cygnets were quickly scooped up with a net and then carefully transferred.Assuming they are healthy, officials at the Cape Wildlife Center said the birds will be kept together as a family unit so they can be rehabilitated and raised. Once they are able to care for themselves, the center expects it is likely they would be returned to the Esplanade Lagoon. Although Boston officials said the euthanized swans were exhibiting avian flu symptoms, some wonder whether blue-green algae may have been to blame — as the severe heat on Sunday could have caused the toxic cyanobacteria to bloom.Wildlife experts said they are still waiting on test results to come back to determine what caused the parent swans to fall seriously ill.The swans' deaths come nearly 13 months after a mother swan that nested along the Charles River Esplanade died suddenly. The Boston Animal Control department later said a necropsy performed on that swan did not provide any additional insight into its death.People who encounter a bird in distress are encouraged to keep their distance, but to take a picture or video and send it to the Massachusetts Division of Fisheries and Wildlife. The distress could be related to the avian flu, and officials say it is critically important to try and track the spread of the virus.