New Delhi, June 6 -- Argentina on Friday said it was expanding its investigation into the origins of the hantavirus outbreak that struck an Atlantic cruise ship last month, sending scientists to trap and test rats in the western province of Mendoza while lab results are pending from the southernmost city of Ushuaia.

Argentine authorities said biologists from the U.S. Centers for Disease Control and Prevention were joining the mission next week in Mendoza.

The rare outbreak on the MV Hondius was caused by the Andes hantavirus, a disease carried by rodents endemic to Argentina and Chile and the only hantavirus thought to be able to spread between people in some cases.

Reconstructing the chain of transmission is difficult work, and Argent...