Karena Herron, 40, was last seen in Sockburn about 4pm on Wednesday, a police spokesperson said.
Yesterday police and family members made a public appeal asking anyone who may have seen her to phone 111.
"Police and Karena’s family have serious concerns for her well-being," the spokesperson said.
Herron drives a black Honda CRV and may have travelled to Oamaru.
If you have seen Herron or have information that may help locate her, call 111 and quote event number P051077441.