MIAMI -- Picture this: you're in line at a grocery store and someone sparks up a conversation.

"They'll approach you and say, 'I can't believe this place isn't going to cash my check. It's $5,000. It's only because I'm illegal in this country," said Robert Taylor with the South American Theft Group Intelligence Network.

The person offers to split the cash if you simply deposit their check in your account. You hesitate. Suddenly, someone else approaches, someone who says they overheard the conversation. They appear eager to snatch up the extra cash. The pressure is on. You jump in and accept the deal.

"Now they're going to the bank with you," Taylor said.

You deposit their check, hand them the cash, and by the time the check bounces, they're long gone with your money.

"These people are highly mobile. They can go from here to Vancouver. It's not a problem," said Taylor.

The SATGIN investigator said these types of scams are happening all over South Florida lately. SATGIN said the scam artists are oftentimes jewel thieves who do this on the side.

"Their surveillance and counter-surveillance is incredible, incredible," Taylor said.

He said your best bet is being savvy. Even if they look really honest, and even if you really need the money, don't bite.

SATGIN said the thieves work in rings. Elderly people are often their biggest targets. If you're approached, SATGIN said politely and firmly say no. Afterward, alert a store manager and call the police.