Hundreds of people have even evacuated from DFAT building in Canberra. Source: News Corp Australia

“The package was a backpack that had been accidentally left there by a staff member,” Station Sergeant Donna Hofmeir told reporters.

“There was nothing suspicious about it apart from the fact it was unattended.”

Sergeant Hofmeir said the owner of the backpack was “extremely embarrassed”.

“It was just a mistake that she’s left it there.”

She admitted that people were jittery after the siege in Sydney, but denied there needed to be a review.

“I don’t think we will, I think our procedures worked very well today.”

The package, which was found shortly before 2pm, forced staff to evacuate the building and drew a response from Federal Police bomb squad officers.

Streets around the DFAT headquarters in Barton were cordoned off, with an alarm bell sounding inside. Hazmat response vehicles also arrived on the scene.

The alarm was raised after a package was located in the building's canteen area, police said.

“ACT Policing is investigating a suspicious package located in the canteen area of the Department of Foreign Affairs and Trade,” they said in a statement.

“ACT Policing provided a coordinated response and cordoned the area as a standard safety precaution.

“Evacuations are underway at DFAT and road closures implemented. Members of the AFP Bomb Response Team are in attendance.”

Evacuated workers congregated under trees in the shade, with the temperature in the low 30s.