Barreto, a clinical psychologist from Fortaleza, had been at a conference in Morocco before arriving in the UK on 2 February.
On 3 March Barreto had been meeting her friend Liliane Silva, with whom she had been staying while working on a research project at the University of Essex in Colchester.
Later that day, Barreto made a 30-minute bus journey to the coastal town of Brightlingsea, and her family and friends have not heard from her since.
Now, Essex Police have been investigating the possibility that Barreto took a boat from the town’s boatyard.
The force has released an image of CCTV footage taken at 00:16 on 4 March, which is the last sighting of Barreto.
They said between 00:16 and 00:36 when the boat was taken from its mooring, Vitoria could no longer be seen on CCTV.
The boat was later found adrift close to Bradwell-on-Sea and returned to Brightlingsea, police said.
At this stage, Essex Police said, there is no clear and identifiable footage of the person who unmoored the boat.
“However, we are exploring the possibility that it is Vitoria,” they added.
Officers have searched “a hugely significant area of land and coastline” along the River Blackwater, Dengie peninsula and River Crouch, along with 2.5km on the southern coast of Mersea Island, Det Supt Anna Granger added.
Granger has also asked owners of boats moored in Brightlingsea to check their vessels, and has called for anyone with CCTV of the harbour area to come forward.