Texas ? An unusually large number of dead bottlenose dolphins have washed ashore near the Gulf of Mexico coastal city Galveston in the past month, and investigators are looking at laboratory slides, satellite photos and anything else they can think of in their search for clues.

About 180 dolphins are stranded in Texas each year, many from January through March – calving season for dolphins, when infants might die during birth or become separated from their mothers and unable to survive alone.

The 47 bodies found recently included many newborns with umbilical cords still attached. The figure represents three times the number found during the same period last year.

“Right now we don’t know what’s going on, but it is definitely significant,” said Daniel Cowan, a pathologist at the University of Texas Medical Branch in Galveston. “Nowhere else in Texas is having this kind of problem. They’re coming in in multiples.”

Investigators theorize that toxins seeping into the water off the Louisiana coast might have killed the dolphins, which were then carried by currents to the Texas shore.

They are also scanning satellite images for algae blooms that might account for the deaths and considering the possibility of morbillivirus, a dolphin virus similar to one that causes canine distemper.