Area prevention manager Brendon Keenan said four people had come forward to give statements after a request last week for witnesses.
"We are going through all of the council records in relation to the tree, that is everything from the occasional pruning to having concrete poured inside it," Keenan said.
"Of course we are working through it with structural engineers."
At the time, Rotorua Lakes Council acting chief executive Craig Tiriana said after concerns from a local tree specialist about bracing, another inspection was done by the council's regular contractor and in late September/early October bracing was replaced and some branch reduction was undertaken.
Tiriana and Rotorua mayor Steve Chadwick said the council would co-operate fully with any investigation into the incident.