Six more dolphins washed up dead on Jersey Shore beaches over the last few days, bringing the total to 52 since July 9, according to The alarming number of dolphin deaths has left many confused.

The dolphin deaths have been declared an "Unusual Mortality Event" by the National Oceanic and Atmospheric Administration, who are investigating the unusually large number of deaths. Officials have not yet determined what has caused the deaths, but possible causes listed by include disease, human activities, and environmental changes.

Photo Credit: Getty Images/Michael Heiman