Casinos in Mississippi, several other states, and Canada were allegedly cheated out of more than $5 million in what authorities say could be the biggest international cheating scam ever.

Federal prosecutors say the cheating ring worked for four years, hitting 18 U.S. casinos, including several on the Mississippi Gulf Coast and in Tunica, Miss.

The feds say they knew it was going on, but it took the help of the Mississippi Gaming Commission to unravel the complex scam.

"Our agents finally figured out what they were doing," said Larry Gregory, executive director of the Mississippi Gaming Commission.

Gregory said the San Diego-based ring, bribed dealers and used high-tech devices to rig blackjack games. Hidden transmitters would predict the order cards would appear.

"They bet great amounts of money knowing what would be the next card, and as a result, winning a lot of money," said Gregory. "In one particular setting, almost a million dollars."

Gregory estimates the thieves netted more than a million dollars from Mississippi casinos, though he won't yet say which ones.

Nineteen people were indicted in California in the bust, facing charges including conspiracy, money laundering, and theft from an Indian casino. He says the Mississippi dealers who took bribes will also face charges.

"I suspect we'll have arrests of some of those dealers in the next week or two," Gregory said.

Gregory says insider involvement is crucial to any successful casino cheating scam. He says casinos could've been cheated out of millions more, if not for the quick work of Mississippi gaming agents.

The charges in this case carry a maximum prison sentence of 24 years.