28-year-old Hugo Da Silva Pires and 31-year-old Catia Feliciano were arrested at Stansted Airport on Friday.
The body of 76-year-old Nelly Akomah was found at around 10.40am last Wednesday at a home on Ladbrook Road.
A postmortem carried out on Thursday was inconclusive, and further tests are taking place to establish a cause of death.
