Many of the people and companies suspected of forming the cartel’s extensive money-laundering network continue to operate, even though they appear, as Mr. Cuéllar just did, on the American government’s so-called kingpin list of cartel operatives and their associates.

Like Mr. Cuéllar, businesspeople accused of working with the cartel live openly here and elsewhere in Mexico, despite American assertions that they are helping to hide billions in illicit profits through an intricate web of ranches, pawnshops, jewelry stores, money exchanges, a racetrack, even a day care center that hummed with the comings and goings of children on a recent afternoon. The day care center was added to the sanctions list seven years ago.

While American and Mexican authorities have conducted some joint investigations and seizures, the kind of close collaboration that led to the capture of Mr. Guzmán last month often breaks down when it comes to dismantling the cartel’s financial backbone. American officials say that they identify suspects based on intelligence from drug, customs and immigration agents, but that to their great frustration there is too little follow-through in Mexico to pursue shady businesses and their owners.

“There is not enough emphasis there on making it a priority,” said Alonzo Peña, a former deputy director at Immigration and Customs Enforcement. “It took the U.S. a long time to focus on money. For a long time, it was ‘Let’s just go after the drugs.’ The U.S. has evolved,” he added, while “Mexico is a little behind the curve and has not made as much of a shift from drugs to money.”