More dolphins have turned up dead along New Jersey beaches.

They were found in Seaside Heights, Long Beach Island and other locations, bringing the number to 58 since July 9.

Director Robert Schoelkopf of the Marine Mammal Stranding Center tells The Press of Atlantic City the dolphins appear to be dying of viral pneumonia, but the cause is unknown.

The federal government has been investigating the cause of dolphin deaths up and down the Eastern Seaboard this summer. Scientists are exploring many possible causes such as disease, changes in the environment and human activities.

The deaths have been declared an "unusual mortality event" by the National Oceanic and Atmospheric Administration.