SAN JOSE — A massive raid of nearly a dozen Vietnamese cafes led by San Jose police and the FBI was the first phase in an ongoing campaign to crack down on illegal gambling and the violence that has followed in its wake.

Tuesday night’s “Operation Omni” was the largest of its kind in the city and ended with the seizure of about 100 video gaming machines spread across 11 businesses in East San Jose, with each machine believed to have had a weekly yield of between $1,000 and $5,000.

While dozens of people were detained as squads assembled from SJPD, FBI, Santa Clara police and the Santa Clara County Sheriff’s Office served federal search warrants on the cafes, no one was arrested in direct connection with the gaming. Now, a more expansive probe will commence to root out the source of the illegal gambling, which in the past has had strong ties to Vietnamese organized crime.

“This is not it,” said Sgt. Todd Trayer of the SJPD vice unit. “We’ve got a lot more work to do. Everything’s in play.”

But beyond the investigative deep dive, San Jose police say they have helped curtail “dozens” of violent crimes associated with the cafes, including at least one homicide, often spurred by territorial struggles over the cash flow. Not to mention the quality-of-life problems — addiction, drugs and possible prostitution — the illegal gambling schemes attract.

“We’ve put a huge dent in the gaming, and we hope we put the same kind of dent in the violence,” SJPD vice commander Lt. Mike Sullivan said.

In fact, it was a deadly shooting that set in motion Tuesday night’s raids, when a 43-year-old San Jose man was killed Dec. 5 outside the Golden King Teahouse, one of the businesses raided Tuesday.

“People are seriously injuring people in and around the establishments, and we believe it’s tied to the gaming,” Sullivan said. “Everything from serious violence to people becoming addicted to gambling. It’s almost at epidemic levels.”

The homicide, which was San Jose’s final killing of 2014, spurred Trayer and FBI agents he had already been working with for more than a year to devise a crackdown strategy.

“That ramped it up,” Sullivan said. “We already had a lot of people getting shot and stabbed. Now people were starting to die, and we had to go full-court press on this.”

By the end of Tuesday night, authorities confiscated dozens of machines valued at about $3,000 each, as well as $125,000 in cash. The businesses searched by police had anywhere between three and 10 machines, often operating in plain sight.

Eight of them were confiscated by FBI agents at the Xinh Xinh Café near Tully Road and McLaughlin Avenue. Nearly 20 patrons and employees were detained, many with zip ties, before they were eventually released.

The operation Tuesday rattled surprised patrons and employees.

“I was shocked,” said a female waitress at Xinh Xinh who asked not to be named out of privacy concerns. “They just barged in.”

A patron at the 168 Café, on Story Road near Lucretia Avenue, objected to what he called heavy-handedness by police as they entered the business.

“They rushed into the store, they’re yelling, pulling guns on customers, tie-wrapping us,” said Vu Nguyen, a 40-year-old San Jose resident who contends he was unaware of any gambling. “I’m playing pool with friends, and I turned around and have two shotguns pointed at me. What did I do wrong?”

Tuesday’s findings will be presented to the Assistant U.S. Attorney overseeing the Northern District of California, who will eventually decide on whether to file indictments in the case. While it was too early for authorities to comment on the broader ramifications of Tuesday’s raids, there is recent precedent in San Jose.

In November 2013 — about the same time the current probe began — the FBI, Drug Enforcement Agency and SJPD served warrants at Vietnamese coffee shops in San Jose, Milpitas and Castro Valley to break up a sizable video gambling ring. Nine people were arrested and indicted in federal court in that case, including an enforcer for the Viet Nation street gang who was accused of using violence and intimidation to push a specific type of machine on shop owners and collect half of the gambling proceeds from each location.

As in that case, the alleged gambling operations revealed Tuesday have suspected ties to organized crime, though specifics were not immediately available, authorities said.

Jim Dudley, a retired San Francisco police commander and current criminal-justice lecturer at San Francisco State, said he encountered similar schemes while overseeing patrol operations in that city’s famed Chinatown, primarily involving gaming, prostitution or massage parlors.

“If it’s a moneymaking enterprise, people don’t want competition,” Dudley said. “Whether it’s the drug trade or extortion, they’re territorial about that.”

Sullivan said he expects Tuesday’s strike to have a ripple effect on others who supplied the gaming machines or had their pockets lined by the operation.

“Yesterday’s warrants will reverberate throughout the city, throughout the state and potentially farther.”

Contact Robert Salonga at 408-920-5002. Follow him at Twitter.com/robertsalonga.