Dozens of Amazon employees were evacuated from a Phoenix warehouse 19 August due to concerns about hazardous materials. Bomb and fire crews were dispatched to the facility after an employee noticed a suspicious bulge on the side of a 55-gallon drum container with pressurised butane gas inside of it.

"Clearly something went wrong with one of those small containers," Captain Mark Vanacore of the Phoenix Police Department said.

Fearing an explosion inside the facility, authorities evacuated the building and deployed a small robot to the scene.

"We were able to get the robot inside the building with a drill equipped on it. Once we were able to do that, we were able to get the 55-gallon drum, actually drill a small hole and alleviate some of the pressure that had built up in that drum," Vanacore said.

Once the barrel was depressurized, firefighters moved in to remove the barrel from the premises. It isn't clear at this point what caused the butane container to bulge or what it was being used for.

The evacuation at the Phoenix facility comes as founder Jeff Bezos faces criticism over what some employees have described as a relentless and hostile work climate within the organisation.