HOUSTON -- Keep children away from the hot grill. Cook your steaks evenly on both sides. And now, there's one more safety tip for those barbecuing this weekend. Make sure your propane tank hasn't been used to make methamphetamine.

It's from a safety alert circulating by e-mail, warning consumers that propane tanks used to make the drug, methamphetamine, are being returned to stores and resold to unsuspecting families.

Some of you asked KPRC Local 2 investigative reporter Amy Davis if this is a real risk to you and your family.

Davis called law enforcement to find out. Investigators with the Methamphetamine Initiative Group (MIG) said using propane tanks in meth labs is not a new phenomenon. They are used to hold anhydrous ammonia -- a gas so corrosive it weakens the tank.

The e-mail sent to Local 2 Investigates goes on to say that "After they are finished with them, they return them to store. They are then refilled with propane and sent back for you and me to buy."

Investigators said the valves of tanks filled with anhydrous ammonia will have blue or green stains on them, such as the ones pictured. It’s something you should look for when buying or renting a propane tank.

Retailer Blue Rhino, which exchanges tanks all across the country, posted the following statement on its Web site.

"Our staff of propane professionals is trained on how to identify a propane tank that may have been used in methamphetamine production. We encounter a very, very low amount of tanks used in meth production -- just a handful out of millions each year. More than likely, anyone engaged in an illegal activity like that will be reluctant to bring their tanks to an exchange center."

One of the officers KPRC Local 2 spoke with said people who use the tanks in meth labs generally steal the tanks they use off of RVs.