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Amazon.com Inc. (AMZN - Get Report) said Wednesday it has started an autonomous delivery service for customers in a neighborhood in Snohomish County, Wash.

The electric delivery system, known as Amazon Scout, consists of six-wheeled vehicles, about the size of a small cooler, that roll along sidewalks at a walking pace, the Seattle-based e-commerce giant said in a blogpost written by Sean Scott, vice president of Amazon Scout.

Amazon said it is starting with six Amazon Scout devices, delivering packages Monday through Friday, during daylight hours. The devices will autonomously follow their delivery route but will initially be accompanied by an Amazon employee.

To use the service, Scott said customers in Snohomish County would order as they normally would and their Amazon packages would be delivered either by a partner carrier or by Amazon Scout. Customers can shop on the Amazon App or website.

"We developed Amazon Scout at our research and development lab in Seattle, ensuring the devices can safely and efficiently navigate around pets, pedestrians and anything else in their path," Scott wrote.

Amazon said it would wait for the results of its test before considering expanding Amazon Scout to other locations. Amazon already uses robots to move inventory in its network of warehouses.

Five years ago, the company unveiled a plan to use small drones capable of carrying up to five pounds' worth of cargo. Amazon said in December that it was still committed to the program.

Shares of Amazon ended off slightly to $1,640.02.