Senior Sergeant Paul Newman said yesterday afternoon officers had spoken with several of Avison's friends, family members, work colleagues and people she had recently had contact with in an effort to establish a clearer picture of her last known movements.
"Our inquiries have so far ledus to Muriwai and there are [Search and Rescue] teams working in the forest near the corner of Coast and Grass Track roads in Muriwai.''
He did, however, point out that officers did not believe any foul play was involved.
"At this point, we have no reason to suspect foul play. However, we are concerned for Carissa's safety, as her actions are out of character.''
Newman said they were still appealing to anyone who may have seen the young woman in the past few days or on the day she went missing.
Police also made an appeal to the woman herself.
"If she is aware of the search, we ask Carissa to make contact with police or family and let us know she is well.''
It is understood Avison's brother, Tyler Avison, was leading yesterday's search near Muriwai Beach.
Tyler Avison earlier told the Herald it was unlike his sister to not be in regular contact and that her disappearance was out of character.
He said he was determined to continue his search for Carissa, saying: "That's all I can really do.''
Avison's disappearance comes two weeks after Torbay woman Patricia Wearn, 73, went missing after leaving her home on Monday, January 16, for an afternoon walk.
Police last week suspended the hunt for Wearn after a large-scale search effort involving police, LandSAR, Navy, Air Force, Civil Defence and Fire Service teams.
Wearn's family praised the search effort from authorities as well as members of the public and the local community who helped.
Can you help? Anyone with information is urged to call Auckland Central Police: (09) 302 6400 or CrimeStoppers anonymously on 0800 555 111.