Nancy Guthrie was last seen on the evening of Saturday 31 January when family members dropped her home. Members of her church noticed her absence at Sunday’s service and notified her family.
Officials have warned she may be in dire health without her medication. Pima County Sheriff Chris Nanos said she was “not in good physical health” but had no reported cognitive issues.
Since 1 February, the FBI said it had received more than 13,000 tips in relation to the case – including 4,000 in the 24 hours after the doorbell camera footage was released.
It is offering money to anyone who comes forward with information about her disappearance and has now doubled the reward from $50,000 (£36,700) to $100,000.