Health officials in New Mexico are investigating the cause of death of an unvaccinated person who tested positive for measles, the state health department said Thursday.

An adult who was infected with measles has died in New Mexico, state health officials announced Thursday, though the virus has not been confirmed as the cause.

An unvaccinated New Mexico resident tested positive for measles upon undergoing a medical examination after dying, but measles so far has not been declared the cause of death.