Zoox has grounded its Atlanta autonomous-vehicle test fleet after workers reported symptoms potentially linked to exposure to toxic gases, including carbon monoxide, carbon dioxide or hydrogen sulfide. The incidents prompted an Occupational Safety and Health Administration inquiry and raise concerns about worker safety as the Amazon-owned company rapidly expands its testing operations.

Up to 40 workers may have been exposed, although Zoox says the number was lower; the company identified 28 employees who travelled in six vehicles with an unexplained odour. Workers reported vomiting, illness and a rotten-egg smell, while Zoox quarantined the vehicles, replaced 12-volt batteries and arranged medical evaluations, but said it had found no carbon monoxide and only one report indicating carbon dioxide exposure.