Deputy Environment Minister Gabriel Quijandria told The Associated Press in an interview on Friday that studies are incomplete but officials hope to complete their research on the likely causes next week.
He said that the carcasses of 877 dolphins and porpoises were found between February and mid-April on the beaches of northern Peru. About 90 percent were long-beaked common dolphins, while others were Burmeister porpoises, Quijandria said.
"The most probable hypothesis is the possibility of an infection with a virus," he said. "There are scientific articles about the incidence of morbillivirus, a type of distemper, in cetaceans in Peru, and that can be ruled out or proven next week."
He said officials don't believe the dolphins' deaths are related to seismic oil exploration work that was carried out off northern Peru between Feb. 8 and April 8 by the Houston-based company BPZ Energy.