EDMONTON -- After being called to nine buy-and-sell meetups that ended in robberies or carjackings, Edmonton police are once again reminding residents to use caution when buying or selling items online.

The reports have all happened since Oct. 8, Edmonton Police Service said.

The suspects have responded to ads posted by sellers on letgo.com, and when the meetup takes place, have threatened sellers with a gun or pepper spray before robbing them of their electronics or vehicle for sale.

“Arrange to meet in a safe, visible and public location, not at your home or in your vehicle, and bring another person with you,” said Det. Calvin Mah of EPS Northeast Division in a written release.

“We also recommend that if the person has a profile photo, ask if they are the person depicted in that image, or ask for a photo or description. If the person who shows up at the meeting point does not match the person depicted, leave immediately. Above all, pay attention to your instincts. If something feels off at any point, abandon the sale.”

On Tuesday, a man was dragged 150 metres after two men came to his home to test drive a car. After they stole the vehicle, and the seller was dragged. He was not injured.

The thieves are described as black male teens between the ages of 15 to 17, operating in groups of two or more. Investigators say the crimes are likely the work of a group of teens who are known to police.

A 17-year-old boy has been arrested and charged with five counts of robbery with a weapon, two counts of possession of a dangerous weapon, and breach of recognizance in relation to the thefts. A second person has been identified and charges are pending.

Anyone with information about the thefts is asked to call police at 780-423-4567 or Crime Stoppers at 1-800-222-8477.