In the far left aisle at Margarita’s Grocery, next to a freezer packed with corn on the cob, tamales and lima beans, customers were offered a product not typically found in convenience stores: slot machines.

Investigators armed with sledgehammers dismantled the four illegal machines at the Temple Hills bodega last week, part of their effort to curtail what they say are a growing number of makeshift betting parlors popping up all over Prince George’s County.

As state and county officials debate proposals for a casino at Rosecroft Raceway or a billion-dollar, Las Vegas-style venue at National Harbor, gambling and games of chance — both legal and illegal — already pervade Prince George’s, whether it’s secret games of dice and poker at nightclubs, church bingo or the scratch-off lottery tickets sold to patrons as they do their wash at a Riverdale laundromat.

In recent months, investigators said they have raided or identified nearly two dozen illegal mini-casinos in the county. Veteran gamblers say there are many more. During a recent raid at a District Heights laundromat, a patron complained to detectives that he had lost $5,000 to the illegal slot machines and that the officers were preventing him from winning it back.

“It seems like every direction we turned — slot machines,” said police Sgt. Laurie Hall, who is in charge of Prince George’s anti-gambling enforcement. “It’s not like a big secret.”

There’s been “a significant increase in the amount of illegal gambling” around the county, said Doyle L. Niemann, a Prince George’s prosecutor who handles gambling cases and also serves as a state delegate. “The more that we’ve got legal gambling to spread around, the more we’ve got people to think, ‘Well, we can do this illegally.’ ”

Prince George’s County Executive Rushern L. Baker (D), a longtime opponent of legalized gambling in the county, last month reversed himself and announced support for “high-end” gaming at National Harbor, the hotel and conference center on the banks of the Potomac River. A casino, Baker said, would create thousands of jobs and generate a gush of new tax revenue.

The first vote on allowing up to 4,750 gaming machines at a Prince George’s casino is expected in a state Senate committee this week.

Opponents argue that gambling is no way to promote long-lasting economic development in Prince George’s and that it would taint a predominantly African American county already struggling with high rates of unemployment and foreclosures.

“It’s like putting crack in front of a recovering addict,” said Sen. Paul G. Pinsky (D-Prince George’s). “We have a lot of people struggling in our county. Why put it in their back yard?”

Yet many of those games of chance, legal or otherwise, are already in their back yards, if not around the corner. And not just in Prince George’s.

Illegal gaming flourishes in many locales across the region. In August, police seized $1 million and 70 gaming machines during a raid at the Eden Center in Falls Church.

In Prince George’s, the illegal offerings vary from place to place. Investigators recently found a cybercafe in Fort Washington with more than three dozen slot machines churning tens of thousands of dollars a week. Other places might have one or two machines. In some cases, the machines are hidden in back rooms, their existence advertised by word of mouth.

A veteran gambler who owns a Prince George’s nightclub said he has played furtive games of dice and poker in clothing stores, barbershops, carwashes, car dealerships and pool halls. “They’ve got whole casinos in a couple of convenience stores, and I can’t believe the county don’t know it exists,” said the club owner, who spoke on the condition of anonymity because the games are illegal.

On a recent afternoon, he said he was among 20 players who gathered in the back of a club playing Texas hold ’em and other card games for more than six hours. “Someone might win $3,000 or $5,000 or $10,000,” he said. “Everyone knows each other.”

Another longtime gambler, a 49-year-old landscaper, said he plays dice and cards twice a week, the games typically starting spontaneously as he and his friends gather. “People come in, and they expect to have a nice time,” he said. “The next thing, you’re gambling, and then the next thing you’re running to the bank and you’re asking yourself, ‘What have I done?’ ”

At Margarita’s Grocery, the illegal machines had names like Crazy Bugs and Monkey Land and appeared to function like Vegas-style slots. Players could insert $5, $10 and $20 bills for credits, then make money winning various combinations of bars, bells, cherries and grapes. A printed ticket allowed them to collect their winnings, if there were any, from the store’s owner. The police seized less than $300 from the machines but found $1,000 in a backroom, the pot from which the owner said he paid winners.

The owner told detectives that the man from whom he got the machines said they were legal. He was being paid in $90 installments to have the machines in his store, he said. Detectives did not immediately charge the store owner, who volunteered to help them build a case against the man who supplied the machines.

Like most places, Prince George’s also hosts legal games of chance.

More than 20 percent of Maryland state lottery tickets were sold in Prince George’s in 2011, the highest percentage of any county, according to the Maryland State Lottery Commission. In Prince George’s, 560 retailers sell lottery tickets, 170 more than in Montgomery County, which has 108,000 more residents.

One of those places in Prince George’s is a video store on Riverdale Road. Behind racks of DVDs, the owner has a table set up and provides pencils for scratch-off players, and for those playing Racetrax, the state’s virtual horse racing game.

Down the street, Jin Kim, owner of the A-1 Laundromat, began selling lottery tickets 15 years ago to give his customers “a diversion” while they wash and fold. Besides various brands of detergent, patrons can choose from 88 scratch-off games.

“$10,000 winner sold here!” reads a note taped to the cashier window, among a blizzard of winning tickets at which players can gawk when they’re not separating their whites and colors.

Philip Carew was absorbed in Keno while one customer loaded laundry. “You give, you give, and one day you receive,” said Carew, who had lost $60 that day.

For 19 years, until 1997, state law allowed charitable gambling in Prince George’s. More than a dozen firehouses and Knights of Columbus halls had casinos where players could bet up to $500 a hand and play blackjack, poker, roulette and baccarat.

But after several casinos failed to pay taxes and critics questioned how much money went to charity, then-Gov. Parris N. Glendening (D) shut the gaming down.

The debate over gambling in Prince George’s has been burbling for a decade, as National Harbor came to fruition and political leaders seized on the potential revenue that a casino at the hotel could generate.

“It’s not just gaming: It’s the live shows, the retail,” Baker said. “It’s everything that will bring in revenue to a place that would attract not just Prince Georgians, but people from Virginia and D.C. and around the world.”

Those who oppose gambling in Prince George’s include clergy, civic associations and the owner of a casino scheduled to open in June at Arundel Mills who fears that Prince George’s will lure his customers away. In Prince George’s, opponents challenged Baker’s claim that the casino would be “high-end,” saying slot machines are inexpensive to play. The county, they said, should focus on trying to lure new industries, along with federal agencies.

“It says something about who we are and what we want to be,” said Rep. Donna Edwards (D-Md.), who opposed gambling in Prince George’s long before she purchased a condominium at National Harbor. “We can do better.”

If a casino were to open at National Harbor, police and prosecutors say they doubt that illegal betting parlors would vanish.

After investigators raided Margarita’s Grocery, they drove to a nearby Exxon station, where they discovered two slot machines and an employee who told them to check the Sunoco station across the street.

A detective walked over and found six more machines, and the team made plans to drop by the next morning with their sledgehammers.