FORT WORTH, Texas -- Police in Garland and Richardson, Texas, are investigating a string of armed robberies connected to purchases arranged on Craigslist.com.

In each robbery, the buyer thought they were getting a good deal on big-ticket items such as televisions or cars. Instead, all three potential buyers were the victims of armed robbery.

Investigators said the potential buyers were told to meet the seller, with cash, at a residence.

In each of the three reported robberies, the unsuspecting buyer knocked on the door and were met with a gun pointed at them.

The residence turned out to be a vacant home that was either for sale or foreclosed upon.

"We want to be very trusting. The best thing for this is probably don't go in the house," said Officer Joe Harn of the Garland Police Department. "If someone says come on in, just continue to knock on the door. One of the things they're depending on is the secrecy of this robbery."

Investigators said buyers should have the seller meet them in a public place, like a bank, where there are a lot of people and cameras around.

Additionally, if you need to go into someone's home, police said buyers should do so with a partner who remains in the car but on the cell phone with the buyer.

Once everything is OK, the buyer can hang up -- but if not, the partner can call the police.