The Auslec building, on the corner of Dalton and Bogan streets, caught alight shortly before 5am and quickly became an inferno.

Parkes Fire Brigade attended the scene but could do little to stop the destruction of the building.

Fire authorities were concerned about the toxicity of the smoke and requested police close shops on both sides of Clarinda Street from The Square to Bushman Street (Star Hotel).

The street was not re-opened until 2.30pm, with some shop owners returning, but others remaining shut.

Major traffic changes were required because of the blaze.

The Newell Highway was completely shut off from traffic and detours were put in place for both north and south bound traffic.

The alarm was triggered at 4.39 and a security firm raised the alarm. NSW Fire and Rescue Service duty commander  Tom Freedom said the building contained electrical gear and merchandise that became toxic when on fire.

He added Hazmat officers checked gas readings in the area and monitored the atmosphere and this underpinned the decision for evacuation of the main section of town.

Members of the Police Crime Scene from Bathurst, Fire Investigation Research and Lachlan Police Area Command are working to find the origin of the blaze.

Investigative officer, Sgt Steve Howard said investigators had already looked at CCTV.

“However, if anyone is aware or saw anything suspicious which might assist us, we urged them to contact Parkes Police on 68629999,” he said.