The evacuated prisoner was kept under guard until being placed back in the cells.
The office affected by the fire was used by the workforce management team and district victims manager. Those staff were yesterday working in other areas of the station.
"Most of the inconvenience is from the water damage to a small number of computers and, on each floor, water has soaked through ceilings, the carpet and into the liftwell," said Mr Le Prou, who was at the station until 3.30am yesterday.
No police files were damaged but some paperwork needed to be dried out. Mr Le Prou said all the police files were held electronically.
Electricians checked the cabling and contractors were called in to help with drying out all three floors of the station.
The cost of the damage was still being assessed but did not appear to be significant.
A fire investigator was called to the scene and, while the case was still under investigation, Mr Le Prou said he could not comment further.