Immigration Minister Scott Morrison says authorities will determine how a group of asylum seekers went undetected on Christmas Island for up to three days after their boat sank.
A total of 27 people were found living on Greta Beach on the island's southeast on Thursday after their boat likely sank on Monday night.
All have been accounted for by immigration officials and Australian Federal Police. One man has since been taken to hospital with minor injuries.
Describing the incident as unusual, Mr Morrison said on Friday a post-incident report would be prepared.
He also defended the inability of Australian authorities to intercept the vessel.
"This is a very big ocean," he said.
"These are very small vessels and these 27 people who are now safe should count themselves extremely fortunate that they did not suffer a far worse fate."
Mr Morrison said the incident should serve as a wider warning to people thinking of getting on boats to Australia because they believe there is a "safety net" waiting for them.
"I am sure that all Australians will be very pleased there has been no loss of life on this occasion," he said.
Opposition border protection spokesman Richard Marles said the failure to know about the Christmas Island group showed flaws in the government's Operation Sovereign Borders policy.
"How, with this focus and discipline, is it possible for asylum seekers to spend three days in Australia without being noticed?" Mr Marles said.
The boat is one of four to arrive in the past week, with the three others intercepted carrying a total of 162 asylum seekers and six crew.
Mr Morrison declined to comment on whether the cluster is linked to Australia's strained relationship with Indonesia.
"I don't think this needs to be over analysed," he said.
Sovereign Borders chief Lieutenant General Angus Campbell said there could be number of reasons why there has been a spike in arrivals, including the weather and ability of people smugglers to bring together prospective travellers.
"We are not in a position to give you a confident statement of why we have a cluster today," he said.
Mr Morrison said it was not the first time several boats had landed in a week.
He said Australia and Indonesia were repairing their relationship after the spying scandal.
"What is important is that the foreign minister (Julie Bishop) was in Jakarta yesterday (and) there is a process that has been agreed between the leaders that is being worked through," he added.
