Dozens of homeowners in Des Moines, Iowa, have been given a nasty surprise by one of the latest real estate industry scams to hit the area.

The homeowners were left bewildered after answering the door to strangers with rental lease agreements for their properties in their hands, claiming they have just rented out their homes. But the problem is, these homes are up for sale not for rent!

Real estate professionals and law enforcement agencies say the scam involves sneaky criminals advertising homes for sale as homes for rent - without the consent of the owners.

The scammers are apparently trawling online listings of properties for sale, then taking the information they find, tweaking it a bit, and then re-posting them on home rental websites, passing themselves off as the landlords. Once they find an interested renter, they produce fake lease agreements and collect a large deposit from unsuspecting victims.

To further trick their victims, they claim to have forgotten or lost the keys to the homes, but instead offer the renters signed permission slips to use a locksmith to gain entry to the homes.

A warning has just gone out to members of the Des Moines Area Association of REALTORS after president Les Sulgrove learned of the latest scam. He's advised members to set up Google alerts for each property they are currently listing, so that they can find out if someone has posted information about their client's properties onto a different website.

"All the scammers need to do is cut and paste the listing information, make one or two changes and that's it," explained Iowa Attorney General office spokesman Geoff Greenwood. "Many people are finding out the hard way that they've been had."