Security firm G4S warned the Immigration Department before the deadly Manus Island riots that Papua New Guinean police were dangerously unpredictable and could start shooting in an emergency.

The firm pleaded with the department to defuse the tensions in the camp by speeding up refugee assessments and talking to the asylum-seekers.

At least one asylum-seeker was shot during the night of violence on February 17 in which 23-year-old Iranian asylum-seeker Reza Barati was killed.

Witness accounts and photographs indicate PNG police fired dozens of shots, some of them at chest or head height. Locally employed G4S guards, who are believed to have carried out much of the violence, were armed with makeshift weapons, not guns.

In a letter dated February 4, Sven Straub, G4S's acting managing director for the southern Pacific region, told Immigration head Martin Bowles the security firm was planning with PNG police to prepare for possible violence.