At least 279 dolphins have stranded across much of the U.S. Gulf Coast since Feb. 1, triple the usual number, and about 98 percent of them have died, scientists from the National Oceanic and Atmospheric Administration said Friday.

Scientists will investigate whether lingering effects from the 2010 BP oil spill and more immediate effects from low salinity because of freshwater flowing from high rivers and a Louisiana spillway contributed to the deaths, said Teri Rowles, coordinator for NOAA Fisheries' Marine Mammal Health and Stranding Response Program.