They were slowly moved from Northbridge to East Perth in a number of separate trips using the police BearCat. The Public Transport Authority has diverted buses around Curtin House as a precaution, and drivers have been asked to avoid Beaufort, Newcastle, Lord and Royal Streets. Scott Higgins, Acting Commander at State Crime, said police would review the way they handle seized chemicals in light of the incident. He said it was not unusual for police to bring chemicals back to Curtin House, but they would review their procedures. It's understood police became concerned about the substance when someone noticed an unusual smell. About a dozen staff were evacuated from the building. Police took advice from ChemCentre. Based on what they could see, it was something we shouldn't be treating the way we had been treating it," Acting Commander Higgins said. They are volatile (chemicals) - it could have been anything from a fire or worse. We just don't know. We're going to look at whether the procedures were followed and look at whether the procedures we have in place are appropriate. Because of the potential volatile nature of those materials, they have decided to use the bomb squad to detonate those materials at Gloucester Park. This is pretty rare. More than 20 police were involved in this morning's operation. Acting Commander Higgins would not comment on the type of chemical seized and said an investigation by the Organised Crime squad was ongoing.