Police say the water was turned off and roads blocked ahead of yesterday's riot on Palm Island in north Queensland, indicating the unrest was premeditated.

The local police station was firebombed and other buildings were damaged in the aftermath of a death in custody.

Police have arrested nine people allegedly involved in the riot.

They have been transported to Townsville because police are unable to keep them in the island's destroyed watchhouse.

Police Commissioner Bob Atkinson says police have some concerns that the riot was premeditated.

"We believe that the water was turned off so there was an inability to fight the fire," Commissioner Atkinson said.

"As well, there were roadblocks put across the road to the airport, including ... a stolen council truck.

"So there are indicators that a degree of planning and preparation went into this, which is of great concern."

Cameroon Doomagee, 36, died last week while in police custody. Locals say Mr Doomagee had broken ribs which caused a rupture in his liver and internal bleeding.

Police say Mr Doomagee died after a scuffle with police during which he and an officer fell to the ground on concrete steps.

A post-mortem into Mr Doomagee's death which police said was consistent with that version of events stirred up anger on Palm Island, sparking yesterday's riot.