Australian Border Force officials have admitted "human error" in their agency's handling of Melbourne refugee Hakeem al-Araibi's case, saying processes that might have prevented him from being detained in Thailand "broke down".
Mr al-Araibi spent two months in a Bangkok prison after having an Interpol red notice issued against him, despite being recognised as a refugee.
He was released last week after a decision by Thai officials not to pursue extradition proceedings.
"Having reviewed the circumstances surrounding Mr al-Araibi, it is clear that human error occurred within the ABF process," Commissioner Michael Outram told a Senate estimates hearing.
"Our officers work around the clock managing huge volumes of transactions, which require manual processes sometimes, to bridge gaps between disparate IT systems, and human error can, and will, continue to occur. But it is rare."
Earlier on Monday, the Australian Federal Police (AFP) blamed a lack of access to the Department of Home Affairs' visa records as a key factor in the detention of Mr al-Araibi.
Commissioner Outram said changes were already being made to try to prevent a similar case from occurring.
Mr Outram told the hearing that ABF staff regularly received red notice information from the AFP which they then needed to cross-check against other government information, a process which could take 14 days.
In Mr al-Araibi's case, Mr Outram said the fact that he had a protection visa should have been passed on to the AFP and the Department of Home Affairs.
"The officer in this case has simply forgotten to send an email, and it's as simple as that," he said.
"And yes the consequences can be quite significant."
Asked if he would like to apologise to Mr al-Araibi, Mr Outram said he could not say whether the mistake directly led to his detention.
"I'm obviously apologetic that an error occurred within Border Force and that is something that we're taking very seriously," he said.
"But to offer an apology for him that would say that I'm accepting that the outcome, what happened in Thailand, was entirely due to that error. I can't say that without speculating."
Systems past their use-by date
Mr Outram said the officer who failed to send the email was not being blamed for the error, arguing staff were dealing with high workloads and outdated technology.
"We are dealing with some legacy systems here that are past their use-by date and we are using manual processes for increasingly large volumes... of people, with human beings at the end of the day being expected to undertake some of those processes," he said.
"If this system was fully automated, of course that would be nirvana for all of us."
The secretary of the Department of Home Affairs, Mike Pezzullo, told the hearing his department was looking at ways of using "sophisticated algorithms and data matching" to automate the process.
"But to accelerate that program would mean that other programs potentially are not funded equally, to an equal level of priority and it's a question of then managing those priorities," he said.