Thieves stole 20 phones during a single Brooklyn concert, The Post has learned — as one expert warns it’s part of a growing trend targeting crowded music venues tied to an international black market.

Cops were called to punk band Hot Mulligan’s performance at the Brooklyn Paramount on Nov. 7 when a slew of unsuspecting concertgoers were seemingly pickpocketed– with the thieves turning off the phones so they couldn’t be tracked, officials confirmed.

Police were called to the Brooklyn Paramount in Downtown Brooklyn during punk band Hot Mulligan’s show, where 20 phones were reported stolen. Google Maps

No arrests have been made to date, but the investigation is still ongoing, an NYPD rep said.

Attendee James Crowley, 31, said he saw multiple people scanning the floor at the Downtown Brooklyn venue, looking for phones that they thought they might have dropped.

“I’ve been going to shows since I was 14…I’ve never seen anything like that,” Crowley said.

One bystander finally said, “I think people are having their phones taken,” according to Crowley.

The incident is the latest in a growing series of mass phone thefts, with the stolen goods oftentimes winding up in China as part of a wildly-lucrative resale market, cybersecurity expert Robert Siciliano told The Post.

The surge in demand for secondhand phones in China began in 2022 as the world emerged from pandemic lockdowns, Siciliano said. Now, the average iPhone is worth between $300 to $500 to thieves — and Chinese resellers can generate up to $5,000 in profit for a single phone stolen from the US.

“The problem is that the devices themselves are getting much more expensive” with iPhone prices nearly doubling over the last decade, he said.

“US-based devices that are stolen can easily be used in countries like China, because their networks aren’t following the same blacklist protocols as we do,” he said.

Lackadaisical prosecution of petty thefts in “mostly blue states,” paired with limited police resources, has led to thieves “realizing that they were literally getting away with crime,” Siciliano said.

Ultimately, only about 5 to 10% of US phone theft cases are solved, Siciliano said, as lengthy investigations require cops to crack password-protected devices and go after the middlemen shipping devices overseas.

“They often don’t have the budgets for that,” he said.

In addition to the Brooklyn Paramount, police reports were filed over the summer for phone thefts at Under the K Bridge (above) and Brooklyn Storehouse, police sources confirmed. Wayne Carrington

In addition to the Brooklyn Paramount, police reports were filed over the summer for phone thefts at Under the K Bridge and Brooklyn Storehouse, police confirmed.

“Had my phone stolen last night [at] Under the K Bridge, both the police and the guy at Verizon said 20+ people have come in today with the same story,” one Reddit user wrote in August.

Another Reddit user described a “whole line of people at lost and found missing phones” after punk band Turnstile’s concert at the same outdoor venue in June.

Turnstile’s summer tour appears to have been rife with pickpocketing complaints, with hundreds of apparent victims leading the band to project an on-screen warning to fans in Los Angeles: “Attention secure your phone K thnx bye.”

“I’ve never seen anything like that,” avid concertgoer James Crowley, 31, said of the mass phone theft at the Brooklyn Paramount. Tiktok/jamespcrowley

A spokesperson for Live Nation, the Brooklyn Paramount’s operator, told The Post there have not been any “notable” theft reports at the music hall outside the Nov. 7 incident, and deferred all further questions to the NYPD.

Monica Minier, a Queens resident who says she attends at least two concerts a week, told The Post her phone was swiped at a show for the first time at Warsaw in Brooklyn on Oct. 9 during rock band High Vis’ concert.

“Multiple” others were pickpocketed in the same night, according to one Reddit thread.

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“It was clearly [part of] a pattern,” Minier, 46, said, noting she stood on a lost-and-found line with a woman whose wallet had been swiped. “I ended up leaving to go home and wipe my phone, and then about five days later … it ended up in China.”

A request for comment from Warsaw’s management was not returned.

Minier, who said she didn’t file a police report, said she is more upset at Warsaw’s management than the thieves – and demands increased, more visible venue security in the future.

“Hire more staff or be more visible,” she fumed, “but I don’t see what’s in it for [the venue] unless people stop going to shows because they’re afraid of this.

The crime trend is “on the rise, and it is global,” said Robert Siciliano, a cybersecurity expert and CEO of Protect Now LLC. Safr.Me

Until then, Minier said she will start using a tether on her phone. Crowley has similarly begun wearing pants with front-zippers to shows to deter thieves.

“It’s really disappointing,” Minier said.

“This feels new, this feels targeted, and it certainly feels like something that, now that it has worked, will continue to get worse.”

Despite the apparent trend, an NYPD spokesperson told The Post pickpocket complaints are down citywide 11%, 1,474 in 2024 to 1,318 this year to date.

Pickpocket crews were busted swiping phones as recently as this summer at the Governor’s Ball Festival in Queens. All were released without bail pending return court appearances.