Australian authorities are transferring a group of asylum seekers who arrived in the port of Geraldton to detention facilities.
Those on board were carrying a sign that said they wanted to go to New Zealand.
It is understood two men in a dinghy first spotted the boat and alerted authorities just after midday on Tuesday, the ABC reports.
Authorities say the boat was undetected until it made it into the harbour and it is not clear how the boat made it so far south before being spotted.
Geraldton is 2240km south of Christmas Island, the usual destination of asylum seekers heading for Australia.
Western Australia Premier Colin Barnett has described the incident as a "serious, unprecedented and unacceptable breach of Australia's border security".
Geraldton mayor Ian Carpenter told the ABC he was unaware of an asylum boat ever reaching Geraldton before.
Steve Branch, who manages the Dome Geraldton cafe, witnessed the boat arrive and told Radio New Zealand it was very unusual for asylum seekers to arrive in that part of the country.
"Most of the boat arrivals are up around Broome which is probably 2500 kilometres north of us."
Australia's Immigration Department said it would send the men to a detention facility in Northam, 460 kilometres south-west of Geraldton, and women, children and family groups would be relocated to a separate unspecified facility.
The department said all 66 asylum seekers will then be transferred to Christmas Island.
Amnesty International says under international law Australia cannot allow a boatload of refugees there to complete their journey to New Zealand.
Auckland-based executive director Grant Bayldon says it will be up to Australian authorities whether they are settled there, or are among 150 refugees that New Zealand has agreed to take from Australia.
Mr Bayldon says more than 90% of all boat people arriving in Australia are found to be legitimate refugees.