UPDATE 2: Oslo police called off their operation around the US embassy, Tuesday, following examination of what turned out to be a practise bomb that personnel forgot.
Whilst it was feared the object secured to the underneath of the vehicle could have been an explosive device, latest reports indicate it was used as part of internal embassy training.
"We're talking about a device that is made with non-hazardous components, but that is supposed to look like a real bomb," police chief of staff Johan Fredriksen tells NRK.
Officers had cordoned off the area, and the operation affected public transport at nearby Nationaltheateret. All those affected were eventually told they could return safely about two hours later.
The false alarm caused the area around the US embassy and Royal Palace to be evacuated earlier today, assisted by the Royal Guards. A large number of emergency service vehicles were sent to the scene after embassy staff had alerted them at 11:22.
“We encourage everyone to stay at least 500 meters away from the area. We ask all come away from the buildings. A bomb team is on site”, officer Martin Todnem said at the time.