Timber and woodchip giant Gunns may have traded while insolvent, the administrators of the collapsed company wrote in a report to creditors.

Administrator PBB Advisory says it needs to do more research to discover the exact date the company became insolvent, but, they wrote, the company was concerned about its solvency at least six months before it entered administration on September 25 last year.

Gunns was placed in a trading halt from March 9 last year until it entered administration.