PARIS — Two of the world’s most notorious digital marketplaces have been knocked out in a one-two punch that officials say yielded a trove of new intelligence about the drug merchants that operate in the hidden corners of the internet.

“This is the largest dark net marketplace takedown in history,” Attorney General Jeff Sessions told reporters in Washington, according a prepared version of his statement. He accused online dealers of “pouring fuel on the fire of the national drug epidemic” and warned that “the darknet is not a place to hide.”

Law enforcement officials in the U.S. and Europe say the operation first took down AlphaBay, whose founder Alexandre Cazes had amassed a fortune of $23 million. Sellers then fled to No. 2 drug market Hansa, only to find out Thursday that police were monitoring it as well.

The double-whammy “meant the Dutch police could identify and disrupt the regular criminal activity on Hansa but then also sweep up all those new users displaced from AlphaBay,” European law enforcement agency Europol said in a statement.

The full month that Dutch police spent monitoring the activity on Hansa meant that international police agencies had some 10,000 addresses for Hansa buyers outside of Holland.

The two-step operation was “psychological warfare,” said Nicolas Cristin, a darknet expert at Carnegie Mellon University.

“It is definitely going to create a bit of chaos,” he said. “There have been takedowns in the past. … And what we’ve seen in the past is initially there is quite a bit of turmoil for like a week or two weeks and then things cool down and people move to other marketplaces that haven’t been taken down.”

Cazes appears to have died in police custody just over a week ago. The Bangkok Post, citing police, said Cazes was found dead in his cell at the Narcotics Suppression Bureau office on July 12, having apparently hanged himself.

Thai authorities didn’t return messages seeking comment Thursday.

Darknet drug websites have thrived following the appearance — and subsequent takedown — of illegal goods bazaar Silk Road. The darknet, a part of the internet accessible only through specialized anonymity-providing tools, is a particularly attractive place for online drug merchants and buyers because they can operate with relative openness.