HOUSTON -- Harris County deputies are sending out a warning after arresting three men accused of pretending to want to buy products on Craigslist but then robbing the sellers, KPRC Local 2 reported.

It's well known that Craigslist has a wealth of good deals and opportunities, but investigators are issuing a warning to sellers.

They said the popular site for online classified ads is also attracting some who are up to no good. That includes three suspects who investigators said posed as potential buyers interested in Rolex watches.

Instead of cash, all the sellers got was an encounter with an armed robber, according to deputies.

Chris Ramirez is an estate agent who sells a number of valuable items through Craigslist. His listings include a Rolex valued at several thousand dollars.

He said meeting strangers to sell expensive items is a risk that many are compelled to take.

"Things are so tight. You have to do whatever you can do to try to make a living," he said. "You still have to go out there and do it, but at the same time, it throws a caution flag up to tell you to make sure that you do things right."

Investigators said one woman did the right thing when she pulled out her BlackBerry cell phone and snapped pictures of one of the suspects. She said he had inquired about her husband's Rolex.

"You get a feeling where something just doesn't feel right and I think that's what she got," Lt. Jeff Stauber said.

Harris County investigators said moments after those pictures were taken, the man produced cash, but they said he then flashed a gun in his waistband.

"He raised the shirt and said 'You know, I'm not paying for this' and off he went," Stauber said.

Investigators said this happened at least six different times in Harris County and in the city of Houston. The three suspects, Nicholas Little, Marcus Winbash, and Mariano Funes, have been arrested but investigators said as many as two others are still out there.

Ramirez said that threat was enough to make him change up the way he does business.

"If (buyers) called about the watch that we have, I wouldn't go meet them right now," he said. "I'd definitely ask them to meet at an office where there's a lot of people around."

Anyone with information on the suspects is asked to call Crime Stoppers at 713-222-TIPS.