Fourteen of 15 Iranian men charged over the riot last September made a brief appearance in a Nauru court on Monday.
Their lawyer had to fly to Fiji earlier on Monday due to urgent family business, a statement from the government of Nauru said.
Magistrate Peter Law told them through an interpreter that each would be expected to indicate whether they wanted to plead guilty or not guilty at their next court appearance later this month.
They are charged with rioting and causing an estimated $24,000 damage to the facility on September 30 last year.
At the time, a spokesman for the Department of Immigration said there had been a “minor disturbance” at the temporary regional processing centre at Topside, Nauru.
There was some minor damage to kitchens, tents and lights, but no staff or asylum seekers were injured.
One of the men who did not appear in court was in Australia receiving medical treatment, a spokesman for the asylum seekers told the court.
The identities of all 15 men have been suppressed by court order.
Their case was adjourned until February 18.