Immigration Minister Scott Morrison said the investigation into the death at a detention center could take several months to "get to some point of knowledge on this," the Australian Broadcasting Corp. reported Friday.
Reza Berati, 23, died this week at a facility on the Papua New Guinea island of Manus after asylum-seekers broke through a fence in an escape attempt. About 67 of them were injured.
Members of the Green party and asylum advocates contend Berati was murdered.
Morrison took responsibility for the violence, saying, "I have been taking steps every day to try and upgrade and get the offshore processing facilities in a far better shape."
Berati landed on Christmas Island in July and was taken to the detention center a month later.
His body will be flown to Iran for burial.
Australia's practice of processing asylum-seekers on Manus and on the island of Nauru has caused controversy.
Australian authorities say the distant centers deter asylum-seekers from undertaking dangerous sea trips directly to Australia. Those trips have killed many people in the past.