From 1998 to 2008, twin brothers Pedro and Margarito Flores ran a nearly $2 billion drug ring that operated in Chicago and other major US cities. They were finally sent to prison in January of this year. 

Toward the end of the operation, however, the DEA may have allowed the twins to keep trafficking their drugs, according to thousands of federal court records, police reports, and court testimony analyzed by Chicago Reader’s Jason McGahan in 2013.

While it might seem shocking that a government agency would let crimes continue, had the twins been arrested immediately, officials never would have nailed two even larger criminals.

On the other hand, it probably would have prevented tons of cocaine from entering US streets.

The twins’ organization grew in Chicago in the early 2000s and at some point began operating within the largest drug trafficking group in the world, the Sinaloa cartel.

Apparently fearing prison time, the Flores twins eventually surrendered themselves on Nov. 30, 2008. Even before that, however, they had teamed up with the DEA to give information on high-ranking Sinaloa leaders in hopes of obtaining more lenient sentences.

While the twins’ cooperation officially began in October 2008, the their lawyer initially made contact with the DEA in April 2008, according to court documents analyzed by McGahan. Between April and the time of their arrest, the brothers’ reportedly trafficked six to eight tons of cocaine into the US.

During his trial, for example, Jorge Llamas, a Chicago drug pusher for the Flores brothers, gave the following testimony under cross-examination:

Q: Let me ask you this: How many times did you pick up drugs or deliver drugs for the Flores brothers from April ’08 through December ’08?

A: Ooh. I don’t know.

Q: Lots of times?

A: Not as much, because … I wasn’t on the day-to-day. So it wasn’t as much as prior ’04.

Q: But it was still going strong, wasn’t it, from April ’08 to December of ’08?

A: Yeah.

The DEA withheld the exact details of an arrangement, if any, it had with the Flores twins prior to their official cooperation. The DEA didn’t immediately respond to Business Insider’s request for comment.

During the trial of one of the brothers’ alleged customers, special agent Matthew McCarthy was asked directly about this issue, according to McGahan. The customer’s lawyer asked him whether the twins provided such worthwhile information that the government would allow them to keep importing drugs during the first part of their cooperation.

“They weren’t in our control,” McCarthy told the court. “We couldn’t stop them.”

U.S. Department of JusticeMargarito Flores

The government, however, would have benefitted from letting the twins continue their drug operation. That way, the DEA could gather information on other traffickers and file charges.

In October 2008, Margarito wore a wire during a meeting at a secret mountain compound with the heads of the Sinaloa cartel: Vicente Zambada-Niebla; his father, Ismael “El Mayo” Zambada, and the kingpin, “El Chapo” Guzman, one of the world’s most wanted drug lords.

On the recordings, Zambada-Niebla asked Margarito to obtain “big, powerful weapons” so the cartel could “blow up some buildings.” Based on these conversations, among other evidence, prosecutors built a case against him.

With the aid of the twins, the DEA also set up a sting operation in December 2008 that put 10 of the twins’ customers, mostly low-level dealers, behind bars, according to the McGahan. But they were small fish compared to the cartel bosses that were almost in the feds’ grasp.

Zambada-Niebla, known as “El Vicentillo,” was eventually captured in 2013. Taking a deal, he pleaded guilty and cooperated with authorities in exchange for a minimum of 10 years in prison. Zambada-Niebla likely flipped on other Sinaloa cartel members, including El Chapo, the notorious drug lord who was subsequently captured in February 2014.

It’s unclear whether the DEA knew the extent of the Flores’ brothers actions during their cooperation. But this isn’t the first time the US government may have allowed illicit activities to happen on its watch.

Documents published by El Universal in early 2014 revealed that between 2000 and 2012, the DEA struck a deal with the Sinaloa cartel itself. While leaders provided information on rival cartels to the US, the organization smuggled billions of dollars of drugs.

El Universal also found that cooperation between the Sinaloa cartel and others peaked between 2006 and 2012 — a period when the Flores twins operated as well as when drug traffickers essentially conquered Mexico.