Complex, sophisticated ‘Ocean’s Eleven’ style burglaries are becoming widespread across the U.S., so much so that jewelers have been officially put on notice.

The Jewelers’ Security Alliance (JSA) and Jewelers Mutual warned this week about some stores suffering major losses as a result of the break-ins, according to a new report from JCK.

Scott Guginsky, the JSA’s vice president, said: “We see burglaries everywhere, from New York to Texas. Some of the hits are in the millions. These are the largest dollar losses we’ve seen in some time.”

“It doesn’t appear like they’re stopping,” said Howard Stone, vice president of global risk services and analytics for Jewelers Mutual. He started noticing the crimes in June, the report says. 

Thefts usually happen on weekends, with gangs dressing as construction workers to blend in, the report says. They use cellphone and Wi-Fi blockers, cut power cables, and wait for backup alarms to drain. Sometimes, they set up hunting cameras as motion sensors.

The JCK report says that the gangs meticulously plan their heists, gathering detailed intelligence beforehand. “They’re all from South America and they are somewhat in communication. But it’s a loose-knit group. It’s not like there’s a [mob boss] John Gotti coordinating everything.”

Guginsky added: “They usually roll into town for a week and do surveillance. They scout out the store, follow the jeweler home. They often send someone in the store during business hours, with a camera on their hat and their shirt, so they have a sense of the layout.”

To prevent burglaries, the JSA and Jewelers Mutual suggest several measures for jewelers: stay alert to suspicious individuals who may be scouting the store or following you, and report any concerns to both the JSA and local authorities, keeping a log of incidents.

They also suggest regularly testing alarms and cameras, updating your emergency contact list, and ensuring contacts are available on weekends and holidays.

Lastly, they tell store owners to build relationships with local law enforcement and mall security to identify store vulnerabilities, the report concludes.